TENSIONS appear to be rising between PPP contractor Tube Lines and Transport for London, as London Underground is poised to explain an alleged discrepancy in upgrade costs for Underground lines. The situation is made more complex by the fact that the two sides are painting very different pictures about the reasons for shortening some Jubilee line closures this weekend.

TfL and Tube Lines have already clashed over the costs of upgrading three lines in the next Control Period, which London Underground says should cost £4 billion. Tube Lines had lost most of its claim for an extra £1.75 billion on top of that, apart from £400 million which had been provisionally agreed by the PPP Arbiter, Chris Bolt.

Now, however, it's emerged that the costs of upgrading the Victoria Line, which is now being done in-house after TfL took over the failed PPP contractor Metronet, are twice as much per kilometre as Tube Lines wants for the Northern. The figures, of £20 million and £10 million respectively, were extracted by Tube Lines from TfL by wielding the Freedom of Information Act. As a result, Mr Bolt has asked for more figures and explanations from LUL.

While longer term funding stays in the melting pot, Tube Lines insiders are annoyed over a statement by Transport for London that some Jubilee Line closures will not be necessary this weekend, because it includes a rebuke to Tube Lines about the number of extra closures which have already taken place.

Tube Lines says it doesn't need the full closures because testing of signalling software over Christmas was much more successful than had been expected, and that at a meeting on Monday it says LUL asked to have this weekend's closures reduced as a result.

London Underground said it rejected Tube Lines' analysis of the comparative costs of line upgrades, and was 'frustrated' that the contractor would not be making full use of the weekend closures which had been available. It also denied that it had asked for the closures to be shortened, and said it would have preferred to see some form of work continue.