The former junior transport minister, who resigned from the government in July to run for Labour's mayoral nomination, made the promise at Labour's annual conference in Bournemouth where she unveiled her manifesto for London.

The Hampstead and Highgate MP and former actress said that initially a Midnight Express Underground and rail service would be opened on the Victoria and District lines between midnight and 4am on Fridays and Saturdays.

But Ms Jackson said she could see no reason why a round-the-clock network would not be possible within a year.

"I think it would be entirely possible - certainly to have the discussions, to have the necessary consultations - for it to be introduced within a year, say, if not less.

"London is increasingly becoming a 24-hour city and certainly the patterns of work are becoming 24 hours."

Glenda Jackson hopes to make London a 24 hour city

She added: "Obviously there would have to be a time when the lines close because they have to be maintained. But I would think at about 4am on a Sunday morning we would be able to do that."

Ms Jackson said the planned Public Private Partnership for the London Underground, plus future expansion of the network, would create the potential for a 24-hour service.

Such a thing as society

Her manifesto entitled There Is Such a Thing as Society also set out plans designed to tackle homelessness in the capital.

Ms Jackson said: "My proposals ensure that there are no more people sleeping on the streets of London. At the moment there are 400 people every night."

The former minister also detailed plans for rapid reaction squads to tackle drug-related crime on some of London's worst housing estates and a Super Bid Office to help the capital win major contracts.

Ms Jackson is one of three main contenders for the Labour nomination, the others, Ken Livingstone and Trevor Phillips have already launched their manifestos but the party itself has yet to announce how it will chose its candidate.