Controversial calls have been made to reduce the speed limit to 20mph across Brighton and Hove.

They have been put forward by Green Party leader Caroline Lucas and Green councillor Ian Davey, who described the move as an essential step to improve road safety.

The idea has been backed by campaign group Brake but labelled "impractical" by motorists.

Coun Davey said the number of deaths and serious injuries suffered on the city's roads was in need of urgent attention and reducing the current 30 mph speed limit would be the best way forward. Latest figures show 6,018 were killed or seriously hurt on Sussex roads last year.

He said: "We want a 20mph limit in all streets where people live, work, play or go to school. That would cover the vast majority of the city. We want the council to start with that and then look at making exceptions where the limit is higher, rather than the other way around."

Several cities have installed similar schemes, with Glasgow recently joining Portsmouth, Hull, Norwich and Leicester.

Coun Davey said the entire area south of the Old Shoreham Road should be made a 20mph zone, with the possible exception of the coast road.

Roger McArthur, from campaign group Traders Against Parking Prosecution, said: "It's not a bad idea, it would certainly be a good thing around schools and a lot of the time you don't really go faster than 15mph around the city anyway.

"The trouble is they couldn't do it on some of the main roads, like the coast road and Old Shoreham Road, it would just be impractical. A lot of them are intolerable as it is."

Several small 20mph zones have already been set up around city schools.

Calls for more have increased since the death of schoolboy Henry Nugent in 2008 as he prepared to cross Chalky Road outside Portslade Community College.

Statistics show the chance of escaping from a road accident without being killed or seriously injured is 97% when a vehicle is travelling at 20mph but only 50% at 35mph.

Several members of the council have recently presented petitions calling for roads in their areas to have limits reduced. Most have yet to see changes.

Councillor Geoffrey Theobald, Brighton and Hove City Council's cabinet member for transport, hinted reduced limits were possible, although he was sceptical of creating 20mph limits on major roads.

He said: "I have recently commissioned a speed limit review of all the city’s A and B roads, which will be finalised this September.

"An experimental blanket 20mph limit scheme in Portsmouth is currently being evaluated by the Government, and further guidance regarding such limits will be issued later this year."