The CBI says easing congestion on the M25 should be a top priority

The CBI said the UK was being let down by its roads and railways and delays were costing the economy �20bn a year.

Business patience and public tolerance was becoming exhausted by the "slow pace" of improvements, it said.

It called for a mixture of public and private investment to boost the planned spending of �180bn in the government's 10-year transport plan by �70bn.

Priorities for business included the M1, M6 and M25 motorways, according to the group's transport spending submission published on Monday.

On the railways the government should focus on greater reliability and capacity for both passenger and freight routes, it said.

We are not calling on the government to break the bank Digby Jones

CBI director general Digby Jones said: "We have a first-rate economy and it deserves a first-rate transport system, not the substandard infrastructure that is currently letting down the whole country."

He said politicians had been "bold" in 2000 by committing to a long-term strategy.

"The original 10-year plan was full of promise but four years and �50bn later there remain profound deficiencies in the UK transport system.

"The catalogue of transport nightmares gets ever longer," he added.

Too much of the transport plan did not deliver the substantial change that industry and the public was hoping for, said the report.

"We are not calling on the government to break the bank," said Mr Jones.

"The scale of transport spending business is asking for would be a relatively small price to pay to deliver to the fourth largest economy in the world the transport system it deserves."

But green pressure group Friends of the Earth stressed that road-building was not the answer to Britain's transport problems.

Its transport campaigner Tony Bosworth said:"Any short-term benefits would soon be lost through the extra traffic these roads would create.