A conservation watchdog has attacked plans for improvement schemes to remove bottlenecks along the A27.

The Sussex Downs Conservation Board is being advised to oppose the road-building until there has been a detailed analysis of its impact.

Consultants drawing up a Government-backed transport blueprint for the South Coast want to remove bottlenecks on the east-west artery.

The proposals call for road improvements at Chichester, Fontwell, Slindon Common, Arundel, Worthing and between Lewes and Polegate.

Most of the work would be in or skirting the Sussex Downs Area of Outstanding Natural Beauty (AONB).

A report to go before the conservation board's executive committee tomorrow says the work cannot be justified without rigorous analysis of its environmental and social impact.

The consultants said removing the worst bottlenecks would improve journey times by about three minutes an hour when the expected extra traffic was taken into account.

Martin Small, the board's planning officer, said: "What we are saying is if you are driving from Chichester to Brighton, is it really going to matter if it takes you three minutes longer balanced against the financial and environmental costs?"

The watchdog's planning committee has already branded the road building proposals uninventive and unimaginative.

Members of the executive committee are also being advised to express concern about separate plans in the blueprint to increase the number of park-and-ride sites outside major centres, such as Brighton and Hove.

But the study's proposals to boost public transport and for better facilities for walkers and cyclists are expected to be supported.

Alan Chapman, of the A27 Action Group, campaigning to stop road widening between Lewes and Polegate, supported the watchdog's stance, saying the consultants had not looked hard enough at alternatives to road transport.

The South Coast Corridor Multi-Modal Study, currently being considered, has to be approved by the South-East England Regional Assembly before being presented to the Government.

Congestion charging should be introduced for all road journeys in the South East to tackle overcrowding on the M25, according to a Government study.

There will be a 33 per cent increase in traffic by 2016 if nothing is done, according to the Orbit Transport Study.

All traffic on motorways and local roads in a band 30 miles outside the M25, reaching Brighton and covering large parts of Sussex, would be charged using meters fitted in vehicles.