Transport for London has lodged a bid to take control of Metronet, the tube infrastructure company, and bring maintenance and repair work on the vast majority of the London Undeground back into the public sector.

A formal offer for Metronet, which collapsed into administration last month, could be made as early as September 30, it emerged today.

In a short statement, TfL said “it is in the best interests of all parties for an exit from administration as quickly as possible”.

TfL added that the move to bring maintenance work back in-house would only be done on a “temporary basis”, but it is understood this could mean as many as two years.

A spokesman for Ernst & Young, the Metronet administrator, said: "We've been told that we are getting the formal Expression of Interest today.

"We look forward to receiving the offer by the end of September It is a welcome development In the meantime, we will continue with our key objectives - the continued safe running of the Tube infrastructure and working towards an exit from administration."

Metronet collapsed into administration after running more than £2 billion over budget. Its staff carry out maintenance and repair work on nine London Underground lines, including the Circle, Victoria and District lines.

Tim O'Toole, London Underground managing director, said: "We strongly believe that the best and most robust way to achieve our ultimate goal is for an early exit from the administration process, to enable Transport for London to maintain the continued safe operation of the Tube network and to mitigate the performance and cost risks that inevitably come with such a situation."

The move threatens to spark a political row between Mayor Ken Livingstone and Prime Minister Gordon Brown.

Gordon Brown was a driving force behind the Public Private Partnership scheme drawn up to attract private sector investment on the Underground despite fierce opposition from the Mayor.

On the day Metronet fell into administration the Prime Minister defended PPP and insisted: "If Metronet pulls out, then another private company will be found to take its place."

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