A campaign group, including two MPs, wants a law to make sure rail passengers have the right to spend a penny.

The group, led by Brighton and Hove city councillor Craig Turton, has demanded the Government creates a new law to ensure train toilets are always available in good working order.

The demand follows a series of complaints from passengers caught out by malfunctioning loos on services between London, Brighton and Littlehampton.

Mr Turton said: "Some passengers have been forced to break their journey and get off trains to use toilets at stations before reaching their destination."

At present there is no legal requirement for rail companies either to provide toilets on their trains or maintain them.

There have been problems for passengers since the introduction of Electrostar trains by operator Southern in 2002.

Toilets have been closed and marked out of order for a number of reasons. They have often been automatically locked by an electronic system, which acts when the toilet waste tanks are 80 per cent full.

Passengers have found themselves locked out on long journeys as a result, some of the toilets remaining out of order for several days.

Brighton MPs Des Turner and David Lepper have already given their support to the campaign and yesterday said they would seek to make it law when Parliament returns in October.

Mr Turner said: "It is a completely unacceptable situation."

Mr Turton will put a motion before his fellow councillors in October, which reads: "This council believes that rail passengers should have a right to flush'."

Mr Lepper will be meeting Southern today and plans to raise the issue.

He said: "It is a real inconvenience for a lot of people and should be addressed."

A spokesman from Southern said it recognised there had been problems but said: "Our toilets are monitored three times a day and any faults are reported immediately, then rectified at the first available opportunity."