London's most expensive loos

These public lavatories are believed to be the most expensive in London. Users are being charged 50p to spend a penny amid fresh flowers and piped music.

The man behind the price hike is the billionaire former Tory treasurer Lord Ashcroft. Carlisle Holdings Ltd, the company of which he is chairman, spruced up the conveniences in Parliament Square, outside Westminster Abbey and by Westminster Pier.

Carlisle Holdings won the £20,000-a-year contract and rebranded the lavatories "Cityloos".

"We don't have any control over how much they charge but it's really worth it: these are the Rolls-Royce of toilets," said a Westminster council spokesman.

But that may be of little comfort to desperate tourists.

"We bring groups of visitors from all over the world to show them the wonders of our capital," said Blue Badge guide Ros Stanwell-Smith. "Now their first impressions will be of rip-off London."

Colleague Simon Rodway said: "We're taking our tourists to St Paul's instead because City of London loos are superb - and free."

Westminster defended its decision to lease out three of its 30 public conveniences, saying the deal would save council tax-payers more than £236,000 a year, and that the council spent ?2.6million a year on public conveniences, more than any other local authority.

"In other parts of the West End we have actually increased the number of free toilets with the introduction of 16 outdoor urinals," said the spokesman.