RMT, London Underground's biggest union has raised fears over the £2bn gap between Tube Lines £7.2bn upgrade cost estimate and the PPP arbiter's valuation of £5.5bn.
The arbiter's initial projection of Tube Lines' costs for the second seven-and-a-half years of its contract, beginning in July 2010, is between £5.1bn and £5.5bn.
The Tube Lines estimate, however, sits at £7.2bn, a big difference of £3.1bn higher or £2.5bn if inflation is taken into account.
The situation has prompted RMT to once again call for the PPP, which it terms "wasteful and inefficient", to be scrapped.
RMT general secretary Bob Crow said that and it is important to understand that 95% of Tube Lines' colossal liabilities are also underwritten by the public purse.
"One way or another there are going to be substantial additional costs if the upgrades are to be delivered, and the obvious question is who will foot that bill," said Crow.
"Subsidy for the Tube has increased 20-fold as a result of the PPP, and Tube Lines has been taking more than £1m a week in profits for its shareholders, and now they are asking for £2bn more than the arbiter thinks their costs should be.
"Once more it is clear that the risk involved in the PPP is being borne by the public. The PPP, like all PFI projects, is a complex scam designed to convert public money into private profit, and these contracts should be brought in-house now," said Crow.
By Daniel Garrun
