Metronet said there would be no compulsory cuts as part of the restructuring and losses would mainly be administration and backroom posts.

A Metronet spokesman said changes would be discussed with union leaders later on Tuesday.

A spokesperson for London Underground confirmed it has not approved the job cuts and that it has consistently said Metronet must improve its performance.

"Staffing levels at Metronet are a matter for them," he said.

It's PPP - the promotion of private profits - that's driving these cuts Gerry Doherty, Transport Salaried Staffs Association

"London Underground has consistently said that Metronet must improve its performance, the maintenance and renewal of the Tube's trains, tracks, tunnels and stations.

"We continue to demand that improvement in performance."

The Transport Salaried Staffs Association, which represents white collar workers on the Tube, said it was "shocked and disappointed" at the scale of the job losses.

General secretary Gerry Doherty said the union believed Metronet was under pressure to make job cuts to appease its shareholders and LU and the union would do all it could to resist the job cuts.

"The private company's primary loyalty lies with their shareholders, not with the passengers using the Underground. It's PPP - the promotion of private profits - that's driving these cuts," he said.

'Hopeful signs'

He said although the Public Private Partnership (PPP) was set up to deliver improvements on the Tube it had failed and said he doubted how it could make things better by employing fewer staff.

Geoff Pope, London Assembly transport spokesman, said "Londoners must hope these changes will bring about the needed improvements to the company's effectiveness in maintaining and upgrading London's Tube system."

Mr Pope said the Tube needed a maintenance regime which is super-efficient and that this "may well be the first hopeful signs".

Metronet has two separate businesses on the Tube and said it was aligning these to bring them closer together.