Midland motorists face at least five months of congestion and diversions this summer thanks to another major roadworks programme designed to cure the M6 pothole epidemic.

In the summer of 2004, an unprecedented, three-pronged resurfacing project saw road gangs on two major viaduct stretches of the M6 through the West Midlands and the Aston Expressway into Birmingham.

The work was brought forward in the Highways Agency programme because of a serious pothole crisis, which saw large dips suddenly open up in the worn-out road surface.

Now, phase two of the project will involve £13.5 million being spent on the opposite carriageway to the one worked on two years ago.

No work is scheduled for the A38(M) Aston Expressway, although northbound drivers will be unable to use the road into the city centre and there will be no access to the southbound M6 from the Expressway.

Work will begin on the two-and-a-half mile southbound stretch on the Bromford Viaduct - part of Spaghetti Junction - and a 960-metre section of the northbound Ray Hall Viaduct, near junction 8 where the M6 meets the M5.

The work will begin after Birmingham's traditional summer sales in July to mini-mise any loss of trade to city shops.

For at least 20 weeks, Birmingham-bound motorists travelling from the south will face queues into the city from junction 5 at Castle Bromwich or be forced to take a long detour to junction 7 at Great Barr.

Neil Dancer, chief highways engineer at Birmingham City Council, has moved to suspend A38 bus lanes along the Tyburn Road to ease the threat of traffic congestion.

But opposition Labour councillors are investigating whether the move is legal without prior consultation with local ward committees.

"We are going to have an onslaught of traffic and we will do our best to avoid utter chaos," Mr Dancer said.

"We have to be mindful of the needs of not only retail interests but everyone else in the city centre."

He warned that any out-break of wet weather was likely to prolong the work, taking it into the lucrative Christmas shopping build-up.

"We are still having meetings on the timing and the detail of the job," a Highways Agency spokesman said.

"We are having a meeting with traders, the city council and contractors next week to go through it and will make an official announcement later."

Jerry Blackett, policy director of the Chamber of Commerce, said it would have been better to have carried out the M6 repairs in one go.

"Surely it would have been better to get the pain over with, rather than have closures going on for years," he explained.