LONDONERS have been warned to expect closures on busy Tube lines for months at a time.

Sections of the Waterloo & City and Northern lines need to be closed for vital repair work to be carried out.

Tim O' Toole, London Underground's Managing Director, told the London Assembly that this would need to happen for vital work to be completed on the network. Proposals are being put forward to shut the lines on several different occasions.

The Assembly's Transport Committee questioned Mr O'Toole and the chief executives from Metronet and Tubelines, the private sector companies responsible for repairing the Underground, about what can be done to speed up improvements on the Underground. The Committee was also told to expect Jubilee Line disruptions around Christmas for engineering works.

Assembly Members heard that contingency plans would be in place for the displaced passengers. But the maintenance firms would need to ensure they had adequate resources to work on the network during the closures and they must deliver on time.

During the meeting, Mr O'Toole stressed that more investment on maintenance was needed from the firms to create a change on the Underground that the public would truly embrace.

He said: "We are not seeing the performance at the levels required in the contracts. These companies need to take risks in overspending to justify repairs."

Mr O'Toole told the Committee that he blamed poor management of the private sector companies for some of the engineering overruns on the Underground, which are delaying commuters particularly during peak times.

Repairs to lifts and escalators are behind schedule and the maintenance firms were accused of not providing the new equipment promised for the work. When asked by the Committee whether the overruns were getting worse, Mr O'Toole agreed.

Tubelines and Metronet conceded at the meeting that some improvements, including station refurbishments, were behind schedule and better management of the repairs was needed.

But they insisted significant improvements can be seen, although there is still more to do. The Committee was told that everyone underestimated the sheer amount of work that needs to be done.

Lynne Featherstone, chair of the Transport Committee, said: "We heard today about some improvements on the Underground, particularly on the Piccadilly and Central Lines.

"But the travelling experience of the millions of Tube passengers is not in any acceptable shape.

"There is an impatience for change on the ground, and it is questionable how quickly London Underground and the maintenance companies can make significant changes on the network. A lot of public money has been spent on the Public Private Partnership contracts between London Underground and Metronet and Tubelines. But there appears to be serious flaws in the arrangements, which are resulting in conflicts between the organisations and delays in getting the Tube up to a 21st century standard."