The six invited to bid for the £40m Paddington Integrated Project are BAM Nutall, Bovis Lend Lease, Carillion Capital Projects, Laing O’Rourke, Morgan Est and VINCI Construction UK.

The latest stage of the Paddington award highlights how vital work on the £16bn Crossrail will be as the construction industry attempts to climb out of recession.

But the long-term future of the scheme was thrown in doubt as a Tory minister admitted the project could be scrapped – just days after the party pledged to support it in the Conservative manifesto.

Shadow London minister Justine Greening told London’s LBC radio that she “cannot guarantee” that the building of the £16bn Crossrail scheme would continue under the Conservatives.

Greening told LBC that she was unable to give “a line-by-line budget on projects across government, including Crossrail. Everything’s up for review but we think it’s important,” she said.

Pressed on whether this meant that a Tory government would allow the Crossrail development to continue, Greening replied: “I can’t give a guarantee that it will continue.”

Asked if this meant it could be scrapped altogether, Greening said: “It’s possible, but at the end of the day we’ve always said that we think it’s an important project and actually the reason this is important is we want to be responsible, so we can’t pretend that we can write an entire budget outside of government.

“We’ve said we’ll do one within 50 days of getting into government if we get elected and we will then provide some clarity and certainty.”

Work to be carried out under C272 Paddington contract includes construction of a shell and core for a relocated Hammersmith and City Line Underground Station, as well as resurfacing works and construction of a roof structure onto an existing reinforced concrete deck known as the Red Star Deck.

The successful contractor will also have to install lifts and escalators, build a new taxi rank, and carry out work for Network Rail on Platform 12 of the main railway station.