Drivers with severe medical conditions face a fine if they park illegally while making a dash for a public toilet.

People suffering from colitis or Crohn's disease occasionally have to answer a call of nature at short notice, and this can mean leaving their car on double yellow lines.

In the past, Sussex Police traffic wardens in Brighton and Hove would turn a blind eye to cars parked illegally if they showed a distinctive yellow sign, following an agreement with the Brighton and West Sussex branch of the National Association of Colitis and Crohn's Disease (NACC).

However, the association has been told that Brighton and Hove City Council, which has taken over parking control, will no longer recognise the sign which means drivers risk a £30 fine if a parking warden sees their car.

Both conditions are inflammatory diseases of the colon and gut which cause digestive problems.

Local NACC chairman Paula Packham said: "We had a system where a person who had to stop in a hurry near public toilets could leave a yellow sign in the window of the car.

"We had an agreement where Sussex Police would either see the sign and leave the car alone, or, if the driver did get a ticket, they had good grounds for appeal.

"We have now been told by the council that the agreement we had will not continue.

"It has suggested we apply for council-issued blue disabled notices to get the protection we need but not all our members meet the conditions that make them eligible to get one.

"The conditions tend to concentrate on mobility and physical restrictions of movement which do not apply with this condition."

The system still works in other areas of Sussex where police are responsible for parking patrols.

About 350 drivers in Brighton, Hove and West Sussex have the signs and Mrs Packham said she wanted to warn drivers coming into the city.

Mrs Packham said: "It will be very worrying for many. People with this condition want to get out and about as much as they can but being restricted like this could cause a lot of problems and put them off going out for a drive.

"We are now planning to go to the council again and ask them if they will agree to the same system we had with Sussex Police so our members can get about without worrying about getting a fine."

A spokesman for the council confirmed the association's signs would not be recognised by parking officials.

He said: "The issue now is whether people with these conditions will be eligible for the blue disabled passes and this is something we are looking into."