A break in a modest, two-star hotel in Paris is around 17% cheaper than its equivalent in London. And four-star accommodation is around 13% less, according to British Airways chairman Lord Marshall, speaking at a conference on London tourism.

The figures are based on prices paid by travellers from abroad, but they are just as relevant to domestic visitors tempted by a few days in the capital.

One reason for the relatively higher prices is a shortage of hotel beds. "There is too much nasty accommodation in the medium and budget price brackets," said Robert Maitland, director of the centre for tourism at the University of Westminster, at the conference.

A third speaker, Selfridges chief executive Vittorio Radice, produced a series of slides of down at heel street architecture. "I know that the transport system is under funded - but we don't need millions to keep the place tidy," he said.

Research by Westminster City Council, which organised the meeting, suggests that while London, arguably, has more to attract tourists than any other capital, the combination of cost with factors such as fear of violent street robbery and pickpockets together with the two biggest deterrents to domestic tourists - begging and litter - may deter some from returning.

The council has drawn up a charter, promising action to address such concerns. It promises, for example, to target "the enviro-crimes that damage London's image", such as unauthorised rubbish dumping, prostitute cards, graffiti and flyposting.

Part of its drive will involve the introduction, planned for September, of 12 uniformed wardens in Leicester Square, which is estimated to attract up to 125,000 pedestrians per day. Though they will not have police powers, the council hopes that the mere presence of the wardens in the area will deter anti-social behaviour. If the scheme works, it is likely to be extended to other so-called "honeypot" areas.