Delays of 15 minutes or more rose to 2,568 during the financial year of 2001 to 2002. This compares to 2,200 in the previous 12 months.

The figures, which do not include stoppages that London Underground had no control over, were announced by the government on Thursday.

Worst affected was the District Line where delays rose from 303 to 431.

Most delays

Metropolitan 444 District 431 Central 378 Bakerloo 253 Piccadilly 248

The Metropolitan Line suffered serious signalling problems that year leading to 444 delays - an increase of 93.

Delays dropped on the East London, Circle and the Hammersmith lines.

And commuters using the Waterloo and City Line enjoy the most reliable service, with just 30 lengthy delays over the same period.

In a written Commons statement, Transport Minister David Jamieson said the increase in delays was "primarily a consequence of problems with ageing assets, especially signalling, including a major problem on the Metropolitan Line during 2001".

The majority of our problems are because we are using very old kit, for seven days a week, 20 hours-a-day London Underground spokesman

He added: "This emphasises the urgent need for the major investment and renewal which our Tube modernisation plans will deliver."

Tube Lines, a private consortium which will upgrade the Northern, Jubilee and Piccadilly lines as a part of Public Private Partnership (PPP) scheme, announced that it aimed to cut delays by 10% within 12 months on 8 January.

It plans to replace signalling systems on the Jubilee and Northern lines by 2011.

A second consortium, Metronet, is due to take over responsibility for the remainder of the London Underground network in the spring of 2003, which is also part of the PPP deal.

A London Underground spokesman said problems on the Metropolitan Line had pushed up average delays but that punctuality was improving.

"The majority of our problems are because we are using very old kit, for seven days a week, 20 hours-a-day," she said.