The Victoria Line carries 511,700 on a weekday

It was supposed to re-open on Monday after two days' work, but parts were still shut during rush hour on Tuesday.

London mayor Ken Livingstone said it looked like "sloppy maintenance work" by Metronet had caused the delays.

Metronet has said damage was caused to an air main in a tunnel, but its workmen had not been in the area.

It is the latest in a series of angry complaints about Metronet's work, which was last month described as a shambles by a furious Peter Hendy, London's transport commissioner.

You've got virtually every dysfunctional transport sub-contractor in Britain all lined up in one consortium Ken Livingstone

Mr Livingstone was a vocal opponent of the controversial public private partnership (PPP) scheme which delegated responsibility for maintenance to two private consortiums.

But he said while things had improved with one of the firms, Tube Lines, it was proving too difficult to hold Metronet to account.

"The problem with Metronet is, it's a consortium of sub-contractors and when they overrun, when they underperform, they have no interest in sacking themselves.

"You've got virtually every dysfunctional transport sub-contractor in Britain all lined up in one consortium - and it's the consortium of your nightmares."

'World-class businesses'

In response, Metronet said it had reduced engineering overruns by nearly 25% in the last financial year, at a time it was carrying out twice as much work.

"We do not accept the mayor's comments, all our shareholders are world-class businesses," a spokesman said.

"We have every incentive to perform well. Mistakes are costly and the penalties significant."

A stretch of the Victoria Line around Highbury and Islington station shut on Friday evening when a man was killed by a train.

It stayed closed at the weekend for maintenance work, but stretches remained shut up until Tuesday morning because of what London Underground described as "poorly managed" work by Metronet.

At one point almost the entire line, between Brixton and Seven Sisters, was shut. It usually carries about 511,700 passengers on a week day.

An LU spokesman said it was "completely unacceptable" and demanded action from Metronet.

But Metronet said the damage may have been caused by an engineering train, operated by a Tube Lines subsidiary, on its way to a worksite.

An investigation is underway.