Metronet is facing a �1bn overspend

The firm said 290 administrative and middle management and 200 temporary and agency posts were to go.

The consortium, which is facing a �1bn overspend on its 30-year public private partnership contract, said it would redeploy at least half the 290 posts.

The Rail Maritime and Transport (RMT) union warned it would be in dispute if any of its members' jobs were cut.

Efficiency

Metronet said it would also withdraw unfilled vacancies and lose jobs when staff left and were not replaced.

Chief executive Andrew Lezala said the firm's efficiency was "a key business objective".

"It's been necessary for us to conduct a further review to ensure we have the right number of people in place, doing the right jobs in our business," he said.

Last week, the firm revealed it was facing a �1bn overspend after seven years into a 30-year public private partnership deal.

Bob Crow, of the RMT, called for Tube maintenance to be brought back in-house.

He said: "We warned months ago the consortium would try to claw back losses from its over-runs by cutting back on work if it failed to wring more money out of the public purse.