Transport Secretary Alistair Darling is expected to say that the best the government is likely to achieve is a figure where congestion in 2010 is no worse than it is now.

A spokesman for the Department for Transport said levels of congestion were higher than forecast two years ago.

Local councils that fail to meet this many targets would be taken over by a government hit squad Liberal Democrats

"This, coupled with higher long-term economic growth forecasts, means that it is now unlikely that we will meet the target set then," he said.

Mr Darling will outline the difficulties in meeting the 5% congestion-cutting target when he reports next week on progress on the government's 10-year transport plan, which was first published in 2000.

But in an interview in the latest edition of The Economist, he said: "You cannot build your way out of this problem. You have got to think of imaginative and innovative solutions."

The reluctance of councils to introduce jam-busting schemes until they see how congestion charging works in London next year, is to be cited as one of the reasons for the problem.

But a department spokesman said: "It is clear that our strategy will make a substantial impact on the levels of congestion in the future.

Road building

"Over the last few weeks Mr Darling has made a number of announcements of significant spending on both roads and rail as part of that strategy."

Growth of road traffic at a time of booming new car sales, low inflation and low unemployment has surprised the government, which has found that its forecasts were somewhat over-optimistic.

Green groups are still reeling from Mr Darling's announcement earlier this week which included a �3bn road building programme as part of a �5.5bn package of nationwide transport improvements.

The package includes �600m extra to local councils for road maintenance; widening the M6 between Manchester and Birmingham to four lanes and the M1 to four lanes through the East Midlands.

The costs of Labour's transport shambles are being paid in misery for motorists and commuters, headaches for British businesses, and damage to our reputation abroad Shadow transport secretary Tim Collins CPRE

Liberal Democrat spokesman Don Foster said the announcement, coupled with the Strategic Rail Authority saying it "is pulling the plug on several rail improvement programmes", had made it a "dire week for passengers".

Mr Darling had "given up on public transport" and "returned to the failed predict-and-provide approach to road building", he added.

Mr Foster said it was "no wonder" the congestion target would be not be met.

It was "yet another missed target on transport from a long list", he said.

Heavily criticised

"Local councils that fail to meet this many targets would be taken over by a government hit squad," Mr Foster added.

"The only way we will ever tackle congestion is by giving the British people the integrated, safe, reliable and affordable public transport alternative they need and deserve."

The 10-year plan has been heavily criticised, particularly by the House of Commons Transport Committee which said the plan "failed to offer a long-term vision of an integrated transport policy" and was based on a strategy that was "inadequately justified and potentially unbalanced".

On Friday shadow transport secretary Tim Collins said "little remained" of the commitments made in the plan

Shambolic failure

And the government had "broken promise after promise" on funding, bypass building and improvements in rail and road safety.

"The costs of Labour's transport shambles are being paid in misery for motorists and commuters, headaches for British businesses, and damage to our reputation abroad.

"Their strategy has been a shambolic failure.

"It is time for a new approach."