Government contracts worth £6.6bn have been awarded to firms including crisis-hit Carillion to build the new HS2 train line between London and Birmingham.

Carillion, in a joint venture with Kier and French firm Eiffage, has won two projects worth £1.4bn. It will design and build two tunnels near Brackley.

Transport Secretary Chris Grayling defended the choice of the construction company, which last week issued a profit warning as its chief executive left the company and its share price tumbled 70 per cent as a result.

Grayling told Sky News: "They're part of a consortium. They're not alone in the contracts and we've had secure undertakings from all the members of the consortium that they will deliver that contract.

"So it's not where one business has to deliver; it's a group of businesses that have to deliver and they've all committed to doing so."

Balfour Beatty and French partner Vinci have won two contracts worth a total of £2.5bn to design and build tunnels further north.

Other firms working on the huge infrastructure project include Skanska Construction UK, Costain, Strabag, Sir Robert McAlpine, VolkerFitzpatrick and Bouygues Travaux Publics.

The TUC welcomed the projects, says The Guardian. Deputy general secretary Paul Nowak said: "It will provide thousands of decent jobs, billions in investment and help close the north-south divide.

"HS2 is a real opportunity for British steel to shine. The next phase of HS2 should bring jobs and investment to the parts of Britain that need them most."

Grayling is expected to announce today what route has been chosen for the next stage of the project, linking Birmingham to the north of England.

The high-speed rail link has proved controversial, with some arguing the money could be better spent boosting existing services, others objecting to the environmental impact on the Chiltern Hills and some critical of the overall cost.

But successive governments have greenlit the project, with construction work to begin next year on the first stage of the project and the first trains expected to run in 2026. It is hoped it will create 16,000 jobs.