Tube infrastructure consortium Metronet said that Keith Clarke, the chief executive of Atkins, would be replaced as its chairman “at some point in the future”.

A spokesperson for the consortium, which includes Balfour Beatty, said “it was never meant to be a long-term appointment”, but that Clarke would not be leaving imminently.

She said his departure was not linked to a report released last Thursday by Chris Bolt, the PPP arbiter, which stated that after three years’ work on the underground Metronet was significantly behind schedule in its work on stations.

Metronet has called on the arbiter to decide which party is responsible for £750m in cost overruns, if its performance does not improve by 2010. Metronet will be informed of the decision before the end of January.

The spokesperson said: “It’s important to realise that the £750m is not an overspend. It is an adverse cost, some of which has already been spent, such as £80-90m on the Central Line fleet, but some is to be spent in the next seven-and-a-half-years, up to 2010.”