The RMT wants maintenance taken away from private companies

Trains will be driven at a maximum of 25mph on stretches of track where there are concerns about safety.

The first day of action coincides with the victory parade of England's World Cup rugby champions.

The Rail, Maritime and Transport union (RMT) is threatening 24-hour strikes and a week-long "go slow" from 17 December if concerns are not met.

RMT members voted for industrial action following two derailments last month at Camden Town and between Barons Court and Hammersmith.

They blame the privatisation of maintenance on the network.

The action, which starts at midnight, could mean fewer trains running and union members will be told to close overcrowded stations.

It will only cause disruption to Tube users travelling to work or Christmas shopping Tim O'Toole, LU managing director

Bob Crow, RMT general secretary, said it would cause "chaos" to Tube services, which he regretted.

He said: "We are hoping that the two days of action will make London Underground (LU) realise that our members feel very strongly about safety.

"We don't want to disrupt people's Christmas shopping, but we are not going to have an unsafe workplace."

The RMT wants safety checks every 48 hours on the track.

It claims since responsibility for maintaining the network was privatised, operations have been streamlined at the expense of safety.

But LU's managing director Tim O'Toole said the "go-slow" would change nothing.

A Northern Line train hit a wall when it derailed at Camden

"It will only cause disruption to Londoners and Tube users travelling to work, or Christmas shopping for their friends and families," he said.

"Since October, we have been working flat-out to improve Tube safety and to demonstrate that to Tube staff.

"We are reviewing Tube maintenance, strengthening fault reporting procedures and have responded, in detail, to every specific safety issue raised at our Tube safety conferences.

But he said he would "continue the dialogue with unions" to try to avoid industrial action.

Thursday's announcement came after an eleventh-hour meeting between London's mayor Ken Livingstone and RMT leaders, in a bid to prevent industrial action.

A final report on the causes of the Hammersmith derailment is due to be released on Friday.