The government is unlikely to reach its target of reducing congestion on major roads by 5% by 2010, the transport secretary Alistair Darling will concede to MPs today.

The admission is due in a report by Mr Darling on the progress of the 10-year transport plan first published by the government in 2000.

It is the second formal review of the plan in just two years.

The jam-busting pledge was one of the targets outlined in the plan which should see around £180 billion ploughed into transport by 2010.

But the department for transport has already admitted it underestimated traffic growth. Mr Darling conceded: "There is no point beating about the bush. We are not going to hit that."

However, the transport secretary said no-one should "indulge in recriminations".

"The investment we are putting in place will stem the remorseless rise we have seen year on year," he told BBC Radio 4's Today programme.

That investment in road and rail improvements must continue, Mr Darling said.

He admitted: "There has not been adequate control over the costs of the railway for a number of years and that can't be allowed to continue."

Mr Darling suggested that cutting train services in response to spiralling costs was not incompatible with government targets on increased passenger numbers.

"What is going to get people on to the trains is reliability.

"The problem is that in the past, the system simply let more and more trains on to the same network with the result that you have bottle-necks, you have congestion on the trains.

"Now what people want, I think, is that when they get on the 7pm from the station and travel to another station, they want to know that they will turn up on time and get there on time."

A department for transport spokesman today blamed traffic problems on majour routes on the slow take-up by local authorities of the option of introducing congestion charges.

Green groups have already expressed fury that the congestion target seems out of reach and were further disheartened by last week's announcement of a near-£3 billion package of road schemes.

"We expect the progress report to downplay all the problems," said environmental group Transport 2000.

"A firm government commitment to charging for road use and support for reallocating road space to pedestrians, cyclists and buses and trams is required."

Another government target in doubt is the 50% increase in rail passengers by 2010. Rail chiefs have hinted that possible subsidy cuts could lead to some services being scrapped, and that rail costs have to be reduced and better use made of the network.

"The 50% increase target is going to very challenging," said the department for transport spokesman.

He added: "Rail is very much a long-term thing. It has suffered from decades of under-investment. Improvements to services will take time."

Mr Darling was also expected to report on rail funding. A total of £33.5bn of public money for the railways over 10 years is now seen as inadequate, and the Strategic Rail Authority will now have to ask more money in a year's time.

The CBI said today it reckoned that an extra £15bn might have to be found to fund the 10-year-plan, with most of the extra money needed for the railways.

CBI director general Digby Jones added: "Business does not want this plan torn to shreds. It would be tragic to squander this once in a lifetime opportunity to cure Britain's transport headache.

"Extra funding is a vital part of the solution. But it is equally important that the government ensures the money spent on the plan is invested wisely and quickly."

Both the Conservatives and the Liberal Democrats have already claimed that many government targets have already been missed.

Shadow transport secretary Tim Collins has dubbed the government's transport policy "a shambles" and both major opposition parties were eager to closely scrutinise today's report from Mr Darling.

Gwyneth Dunwoody, Labour chair of the Commons transport select committee, voiced sympathy for Mr Darling.

"He came in just at the time when he expected that the large sums of money being spent would be beginning to produce results," she told BBC Radio 4's Today programme.

"The difficulty is that, of course, all sorts of other problems have kicked in at the same time."

Mrs Dunwoody warned cutting back train services after increasing investment in rail would anger passengers.

"If you make sure you have got value for money, people will go along with it," she said.

"What they will not do is have the disruption, the dirt, the upset, get more and more expensive tickets and then be told that the only way out of this is to cut 20% of your services.

"No. I think not. You start again."