Britain's railways have failed to show any meaningful signs of improvement over the last 12 months, according to the Strategic Rail Authority.

Figures released on Monday revealed that performance had not changed despite millions of pounds being invested.

Transport secretary Alistair Darling described the findings as "disappointing" but claimed there would be improvements.

Darling claimed the problems stemmed from the final days of Railtrack which the new management at Network Rail was beginning to put right.

"The performance today has been disappointing. It should have been a lot better, but there is now a realism in the industry," he said.

"When I took up my job a year ago it wasn't there, people were blaming each other.

"We've got a plan, we're getting on with it, we're getting a grip of the situation, we're sorting out the problems and that's why I'm optimistic about the future of the railways."

He warned passengers would be likely to feel the brunt of costs through fair increases rather than hitting them with tax increases instead.

The transport secretary revealed the Strategic Rail Authority would also be announcing plans to tackle poor performance as well as further details on the improvements to the west coast mainline project.

Included would be plans for the next eight years and how it would take on failing rail firms that have not improved punctuality.

The revelations over the state of Britain's railways came on the day a think tank warned the country's roads will be gridlocked within 10 years unless there is a rapid increase in road charging.

Traffic will grow by a fifth by 2010, according to the study by the Independent Transport Commission.

It also predicted the average traffic increase in England could be limited to four per cent by 2010 if fuel duty was scrapped and replaced with a charge for road use based on the congestion and pollution caused by each journey.

ITC head Sir Patrick Brown said drivers would not suffer financially under a congestion charge and less traffic would mean better public transport, he claimed.

"In 10 years time there will be real gridlock on the roads if nothing else is done," he said.

"You can have massive improvements in the public transport system in the sense of buses if you make the roads uncongested.

"At the moment people don't get on buses in the cities like Birmingham and Manchester because they are slow, unreliable and they don't provide a service.

"But as we have noticed in London in the congestion charging zone, the buses run beautifully."

Stephen Joseph, director of campaign group Transport 2000, welcomed the report."Something like a congestion charge is inevitable," he said.

"There are a lot of other things that need to be done, but some element of this is inevitable because we can't carry on as we are."