Open-air mobile toilets are to be used at London tourist hotspots in a battle against a "serious problem" of street fouling.

It is hoped the loos will stop people urinating against walls and doorways, which can lead to corroded buildings and health hazards.

It comes as Westminster City Council, which is piloting the �11,000 trial, prepares to slap �500 fines on offenders with new by-laws.

The plastic urinals, which still give people privacy, will appear in Soho and Covent Garden from Friday.

Dutch experiment

A council spokeswoman said: "Four men can use the one urinal at any time. It is public but also private.

"If they are successful, we will extend the scheme."

The urinals are based on an experiment in the Dutch cities of Amsterdam and Apeldoorn.

The scheme will be piloted in Covent Garden

According to the spokeswoman they have been "well received" since their introduction by local authorities.

The mobile urinals will be open on Friday and Saturday nights between 7pm and 8.30am, before being removed for cleaning the morning after.

Two fixed urinals will also be installed in the West End in September and will be open from 7pm to 8am every day.

Social responsibility

Michael Wylde, of the Covent Garden Community Association Environment, said the urinals are targeted at "men who urinate anywhere and everywhere in the West End".

"This is a serious problem, I am pleased to say that Westminster has come to the rescue. Hopefully this will catch on with more to come," he said.

Judith Warner, chairwoman of Westminster's environment and leisure committee, warned: "These urinals will only work if people become more socially responsible for their actions."