The penalties have been proposed in a consultation paper published by the Home Office, which proposes to make it a criminal offence to leave the advertisements, known as "tartcards", in phone booths.

About 14 million cards, which often include sexually explicit images, are left in public telephone boxes each year.

'Bad impression'

Home Office Minister Paul Boateng said previous attempts to clean up the cards through laws covering littering, criminal damage and indecency, had only led to the people who distribute the cards changing tactics.

14 million cards are left every year

He said: "Prostitutes' cards in telephone boxes are offensive, create a bad impression with foreign visitors and can be a bad influence on young people.

"Those who place the cards in phone boxes can be threatening or violent towards the members of the public and phone box cleaning teams.

"The law should be able to deal with this nuisance - but at the moment it is failing."

The changes backed by the Home Office would make the posting of any unauthorised advertising in phone boxes illegal.

The powers would be locally based, so that they would only be implemented in areas affected by the prostitutes' cards.

The problem began in the mid-'80s in the red-light areas of London and now involves around 1,000 pay-phones in the centre of the capital.

In Brighton and Hove on the south coast, one million cards a year are collected by BT and the problem is beginning to emerge in other cities.

Two years in jail

The consultation paper also suggests the problem could be tackled with a specific criminal offence of advertising sexual services in phone boxes although this could lead to problems of definition and enforceability.

It also suggests civil action could be taken by designating prostitutes' cards as a "nuisance".

Breaches of a civil injunction to stop posting the cards would be a contempt of court, with an unlimited fine and a possible two years in jail.

This option could be used with the criminal offences.

Call barring could be needed to solve the problem

The paper also says a multi-pronged approach could be necessary to address the problem, in particular the use of call-barring by telephone companies.

BT has introduced a policy of barring incoming calls to numbers advertised on cards, but so far this has simply led to prostitutes switching to other phone companies.

The company, which spends £250,000 a year on the problem, is also seeking the power to bar calls from its own phone boxes to any numbers advertised on cards regardless of the phone company involved.

The English Collective of Prostitutes has warned that the measures will cause "serious" problems.

Using the cards means women do not have to work on the street and are independent of pimps, meaning they are safer and freer from exploitation, the collective says.