Major roadworks planned for the Midlands' busiest motorway this summer could cost Birmingham's economy #10 million a day, business leaders have warned.

Companies and commuters have been told to prepare for congestion to worsen on the M6 this summer during the second stage of a roadworks blitz aimed at combating an epidemic of potholes.

It coincided with more concerns expressed by the business lobby about the possibility of congestion charging in the region, with officials warning it would not work unless there was major investment in public transport infrastructure.

Details of the #12 million M6 scheme, which will run from July to December, were revealed by the Highways Agency yesterday. Two years ago, pothole repair works were carried out on the northbound carriageway between Junctions 6 and 5 (Bromford viaduct) and southbound between Junctions 8 and 9 (Rayhall Viaduct).

From July, the second half of the programme will see major work on the opposite side of the carriageway. It will involve the closure of: 

* the slip road leading to the A38 Aston Expressway from the northbound carriageway of the M6

* the A38 slip road heading towards the southbound M6 from July to early September, along with the slip road at Junction 9

At both locations traffic will be diverted through two lanes in each direction with a contraflow.

During the early stages of the previous project, the Chamber claimed congestion cost businesses #10 million a day.

John Lamb, from the Birmingham Chamber of Commerce, said: "We can guess that the disruption will cost business the same as last time. It seems to be an annual event and in the current climate is not needed. We do understand that it has to be done and it is essential that roads are kept in good shape.

"But we would anticipate that as there are no new roads being laid, and we have a poor public transport system, congestion will be inevitable."

As part of the repairs, more than 80 potholes on the motorway have to be fixed immediately because of their potential danger to traffic.

The Highways Agency said the work had been timed for the summer in a bid to reduce the impact on motorists because traffic flows are lighter.

Spokeswoman Sarah Churchill said: "The only solution is to carry out major restructuring. If we do not do this, the potholing will become worse, especially as we move into the winter weather.

"We have used the same strategies that we used last time. We did get disruption then, but we have done everything we can to try to reduce that this time."

Meanwhile, a meeting in Birmingham last night was presented with research showing congestion charges, or road pricing, could only be implemented if cheaper, more frequent and more reliable public transport was in place in the region.

The research was carried out by the Institute of Chartered Accountants (ICAEW) and unveiled at a debate on congestion charging at Birmingham's Botanical Gardens last night.

An overwhelming majority of the audience rejected the idea of congestion charging. However, a large number did support a national road pricing scheme if the money was reinvested into the road system and there was a dramatic reduction in road duty.

The Government has put forward plans for a pilot road pricing scheme for the region in exchange for investment in public transport schemes.

But Robin Birn, head of consultation and research at the ICAEW, said businesses were confused about what schemes were likely to go ahead.