RMT said it was seeking assurances that the government would not allow a land-grab or other asset-stripping and that the Eurostar workers' pension fund would not be undermined by a change of ownership.

The union also called for the £3.7 billion of public money invested in the company to be safeguarded.

"Huge sums of public money have already been invested in underwriting what is an important national infrastructure project and that money is not the government's simply to give away," RMT general secretary Bob Crow said today.

"The last thing we need to see is yet more public money ending up subsidising the profits of the government's big-business mates.

"If the proposed buy-out does not include provision for repaying every penny of the £3.7 billion of public money shoring the company up we will be entitled to ask what is going on.

"The closeness of Adrian Montague to the government has raised fears that this is effectively already a done deal, and we will need to keep a very close eye on the detail if it goes ahead

"Our Eurostar members are rightly concerned that any buy-out will not adversely affect their section of the Railways Pension Fund, and we will be seeking assurances that our members' pensions will be secure," Bob Crow said.