All slamdoor trains are meant to be scrapped by the end of this year

A National Audit Office (NAO) report found although the new trains brought benefits, most were delivered late.

Sometimes they were less reliable than the rolling stock they were replacing.

It means the December deadline for phasing out slamdoor trains is unlikely to be met, the chairman of the Commons Public Accounts Committee has warned.

Thousands of passengers are condemned to continue travelling on the overcrowded, grubby slam-door trains which they had been led to expect would soon be replaced Edward Leigh Public Accounts Committee Chairman

Edward Leigh said the NAO report had revealed a "catalogue of blunders".

"Thousands of passengers are condemned to continue travelling on the overcrowded, grubby slamdoor trains which they had been led to expect would soon be replaced," the Conservative MP went on.

The Strategic Rail Authority, which oversees the introduction of new trains, must "bang some heads together to get results", Mr Leigh added.

But SRA chairman Richard Bowker said the report highlighted the legacy of the past.

"We're getting to grips. We're sorting these problems out," he told BBC Radio 4's Today Programme.

"These new trains are more sophisticated; they have a lot more features on them for passengers which people want like air conditioning.

"The trains are having teething problems but what's important is the rate at which these problems are being sorted out," he added.

Investment

The NAO found some of the new rolling stock arrived with operators between a month and 26 months late.

There was no capacity to test the trains before they were brought into service, which meant they were often less reliable than the ones they replaced, the report added.

More needed to be done, it added, to put in place a realistic timetable for introducing new trains.

The NAO focused on the work of the Strategic Rail Authority, which was set up in 2001 to let and manage passenger franchises and oversee major infrastructure projects.

But it found no evidence the authority's predecessor organisation, the Shadow SRA, which set the slamdoor replacement deadline, had checked whether it was viable.

Often, [new trains] are less reliable than the old trains they have replaced National Audit Office Train firm to replace new fleet

The SRA pointed out that under its stewardship the average age of rolling stock will have fallen from 23 to 14 years by 2005.

Of the 4,540 new vehicles ordered since 1997, over 2,020 were now operational, it added.

The Department of Transport said �1bn was being spent to ensure new trains would be introduced, with 40% of all trains being replaced in five years.

But, a spokesman added, it was still dealing with the effects of a "botched privatisation" and insufficient investment.

Rail expert Christian Woolmar blamed a lack of co-ordination across the network.