Britain has a great reputation for affordable accommodation - it has spearheaded the boutique hotel revolution, and when it comes to staying with the locals and enjoying all the benefits that can bring, the British B&B takes a lot of beating.

But it's one thing for a hotel room, booked, perhaps, for a romantic weekend getaway, to disappoint because the view is of the carpark instead of rolling hills, or you don't like the floral wallpaper and swirly carpet. It is quite another for it to fail you on grounds of cleanliness. In the same way that those who choose to fly on a budget airline deserve to be accorded the same safety levels as those who pay full whack on scheduled flights, people who have bagged a bargain city centre room (and the Which? report fingers the worst offenders as being in central London and Manchester) for under £100 a night should still be able to expect the same standard of hygiene as those in a five-star hotel - if not the comfort, service or décor.

A room is either clean or it isn't. I cannot tell you how many spotless rooms I have stayed in - but I can certainly remember the one that wasn't, in Cambridge, which reeked of stale smoke, had no natural light and when a room service sandwich arrived it had been made with mouldy bread.

However, Visit Britain's latest figures show that less than 5% of accommodation it inspects get a 100% score for cleanliness. It won't be enough this year to cut room rates. These institutions need to invest in some white cotton gloves (it's how the real pros check for dust), some powerful bleach and clean up their act.

Have you stayed in a less than spotless hotel room ? where the carpets appear to wear the remains of last night's party or the toilet hasn't been cleaned properly? Let us know

? Sally Shalam is Guardian Travel's hotel reviewer

Now that the boutique hotel trappings of Egyptian cotton sheets, walk-in slate showers and elegant dark wood have been adopted by even the most modest places to stay, tourists might think we live in an era of luxury for all.

But a report from undercover hotel inspectors published today reveals a grimier reality beneath the surface of the British hospitality industry.

Researchers for Which? Holiday magazine who checked into 16 budget hotels in London and Manchester pretending to be ordinary guests found mouldy mattresses, stained duvets and dirty toilets at some leading chains. Ibis performed "particularly badly", the team said, and Travelodge was also criticised in their report.

The results of the investigation come as domestic tourism is preparing for a boom, with credit-squeezed holidaymakers tightening their belts, and cost-conscious business travellers trading down.

Despite these favourable conditions, Which? said it was concerned by the standards of cleanliness it found.

The team, consisting of a researcher and a microbiologist, said their "most disturbing" discovery was a mattress in the Ibis on Charles Street, Manchester, which was so badly soiled that the cover had started to fray and mould had begun to grow. A duvet at the Ibis on Portland Street in the same city was stained, with the microbiologist suggesting one of the marks was blood. There was "something sticky on the bedside table surface", the report added.

The Ibis Euston in London was home to the dirtiest toilet the researchers found, with urine and faeces around the edge of the seat and urine streaked down the pedestal, according to the report. On the bedroom floor they observed a stray fingernail and food debris.

Which? said bathrooms at the five Travelodges it visited were unclean and it was concerned that bacteria found in four of the rooms could indicate poor cleaning.

At the chain's Gray's Inn Road hotel in London, inspectors found "appalling" levels of dust under the bed. "It was so bad that when we kicked the carpet, dust rose before our eyes and our consultant's footprint was left outlined on the floor. The wall behind the curtains was also thick with ground-in dirt, which contained a handprint streaked down the wall."

At Blackfriars Street in Manchester, a Travelodge room had mould around the bath, and in Ancoats Street the inspectors found a stained duvet and mattress.

Which? Holiday's researcher, Amanda Diamond, said the results were a surprise. "When we set out to do the report we really thought we would find nothing; we thought it would be more to do with comparing budget hotel chains, given that the market is growing and more people are looking for cheaper rooms in the current economic climate. We took a microbiologist as a precaution. We certainly didn't expect to find rooms in such poor condition."

Research published by Travelodge this week suggested that more than half of Britons plan to stay in the UK for their summer break this year. Overseas travel declined by 10.5% in October, according to the Office for National Statistics, and trips to Spain - British tourists' favourite destination by far - fell 15% last year, the Spanish tourism ministry said.

Whitbread, which owns Premier Inn, plans to double its rooms in the UK to 55,000 within five years while Travelodge hopes to have 55 new properties by 2015 and raise capacity from 24,600 rooms to 70,000 by 2020.

Lorna Cowan, editor of Which? Holiday, said: "Although this investigation was just a snapshot, it does raise concerns about the cleanliness of some budget hotel chains. It's clear from our research that some of the hotels are getting it right when appropriate cleaning methods are being used. Paying guests should be guaranteed, at the very least, a clean room.

"There doesn't seem to be one single accepted standard for hygiene in hotels across the UK, and we would like to see this change."

An Ibis spokesman said: "Ibis treats matters of cleanliness and hygiene as critically important. We were, therefore, very disappointed to see the results of the investigation which showed standards that are totally unacceptable to us.

"We have clear procedures in place to ensure that housekeeping standards are to the highest levels. Clearly the Which? investigation indicates that those procedures are not being implemented in some cases and we have taken immediate remedial actions to ensure we deliver the standards of cleanliness that all our guests have the right to expect.

"We have submitted the results Which? obtained to an established independent health and safety consultant, who has confirmed that nothing in those results constitutes a danger to public health."

A Travelodge spokesman said the chain rejected any suggestion that Which? or its customers should be concerned at the level of bacteria found. "According to a leading independent microbiologist that reviewed Which's findings, the levels of bacteria found were so low that they could not cause any health risk whatsoever.

"With regard to the isolated incidents of dust, we would like to reassure customers that we immediately remedied these cases through strengthening of cleaning procedures and superior cleaning materials.

"Our six million customers should always enjoy a good quality stay, so this report has helped us by highlighting a handful of cases where we needed to improve."

A new £4.5bn international rail exchange for Heathrow airport is being backed by the transport minister, Lord Adonis, as a top contender for a series of projects that will follow the approval of the £16bn Crossrail scheme for the capital.

The Department for Transport confirmed yesterday that the scheme had high priority among a number of projects that include a new high-speed rail link for London to Manchester and Leeds and the electrification of the Great Western railway to Plymouth and Swansea. The international rail hub, which has already been put forward by the Conservatives, is not, according to the ministry, being offered as an "environmental sweetener" to persuade opponents to accept the building of a third runway for Heathrow. A spokeswoman said yesterday: "The decision has nothing to do with the third runway. It is part of another major review on high-speed rail projects being conducted by the ministry." All the indications are that Downing Street will approve the third runway, with a decision expected later this month when parliament returns from the Christmas and new year break. It was to have been announced before Christmas, but there is strong opposition in the cabinet to a third runway led by Hilary Benn, the environment secretary, and Ed Miliband, the climate change secretary.

Adonis made it clear that the rail hub, which would become the largest station in the United Kingdom, was "attractive". It would be linked to a new high-speed north-south railway, cutting journey times between Heathrow and Manchester and Leeds. He told the Sunday Times: "It's vital that we have an integrated approach to planning new rail capacity and any new airport capacity that is also required."

The transport department is one of several ministries putting forward long-term infrastructure projects to the Treasury, including wind farms, and expansions of broadband and the nuclear power programme. Gordon Brown's more modest short-term boost for infrastructure projects includes flood defences and motorway widening schemes.

The government will face strong opposition from the Conservatives, who want to stop the third runway, from Boris Johnson, the mayor of London, who wants an airport in the Thames estuary, and from Tory-controlled Kent county council, which wants to open an international airport in the deprived part of east Kent and link it to the Channel Tunnel rail link.

Public opinion is still opposed to the third runway at Heathrow, with the latest opinion poll released by Greenpeace showing that Labour could lose four seats - Battersea, Ealing Central and Acton, Brentford and Isleworth, and Hammersmith - over the issue. Theresa Villiers, the shadow transport secretary, yesterday said: "A new rail hub at Heathrow should be an alternative to a third runway, not a sweetener for it."