A bypass on the congested A27 through Worthing has been all but ruled out after it was revealed it would cost at least £1 billion.

The bill is equivalent to the total budget for all major transport improvements in the whole of the South East for six years.

As a result, there is no realistic chance of a bypass being built over countryside either north or south of Cissbury Ring, near Findon, for at least 20 years.

In fact it may never be built, according to West Sussex County Council's A27 working party.

The Argus exclusively revealed on Monday that the working party had spent two years looking at ways of relieving congestion on the Upper Brighton Road and Arundel Road, which form the A27 in Worthing.

Ideas include increasing the number of lanes from two to three and constructing flyovers at the Offington and Grove Lodge roundabouts, which "may require demolition of some properties".

The suggestions sparked anger from Worthing Borough Council leader Keith Mercer, who said: "This is just tinkering."

He believed the only solution was a real bypass, in a tunnel north of Cissbury Ring, an ancient Iron Age hill fort.

Coun Mercer said some of the cost could be offset by making it a toll road.

However, the scheme would spark uproar among conservationists who have fought long and hard to protect the Downs from development.

The Worthing section of the A27 has for decades been described by experts as the worst bottleneck on the South Coast between Folkestone and Honiton.

Traffic travelling into the town from both east and west is channelled from four lanes into two between Lyons Farm and Swandean.

Councillors believed grass verges would be swallowed up but could not say whether some front gardens might be compulsorily purchased.

The Argus was also told the working party could not decide whether the third lane should serve east-west or west-east traffic.

The suggestions will cause concern among people living alongside the A27, who have been blighted by past schemes which, after years of wrangling, never went ahead.

Twice in the past homes were boarded up to await demolition, causing property prices in neighbouring roads to slump, only for the "improvements" to be shelved.

The working party also looked at park-and-ride, with Lyons Farm, just off the A27, and Brooklands, on the seafront, possible locations.

It is expected to publish its report later this month.