Tube Lines and one of its co-owners, Bechtel, have been labelled as "clowns" by the owner of the O2 arena after the PPP contractor admitted that it cannot deliver an upgrade of the Jubilee line on time. The O2 has hosted concerts by the Verve, the Rolling Stones and Led Zeppelin.

But it has been hamstrung by more than 100 Jubilee line closures over the past two years. David Campbell, chief executive of AEG Europe, the arena's owner, said Tube Lines' claims that it could complete the upgrade by January had "zero credibility" and said "clowns" were behind the delays.

"They have not delivered on any deadline over the past two years. So any deadline they give has not got any credibility behind it." Campbell warned that other Tube Lines' upgrades, with the Northern and Piccadilly to come over the next decade, could could cause significant disruption as well.

"It does not bode well for the other lines."