Image copyright HS2/Grimshaw Image caption An artist's impression of the proposed HS2 Euston station

The winners of £6.6bn worth of contracts to build the first phase of HS2 between London and Birmingham have been announced by the government.

UK firms Carillion, Costain and Balfour Beatty are among the consortiums who will build tunnels, bridges and embankments on the first stretch of the new high speed rail line.

The contracts will support 16,000 jobs.

The final routes of the Manchester and Leeds branches of HS2 are due to be announced later.

It will include a decision over its path through Sheffield.

Transport Secretary Chris Grayling said: "As well as providing desperately needed new seats and better connecting our major cities, HS2 will help rebalance our economy."

But critics say the £56bn project will damage the environment and is too expensive.

The first trains are not expected to run until 2026.

'No doubts'

Mr Grayling told the BBC's Today programme that the high-speed rail network will be "on time, on budget" and the government has "a clear idea of what it will cost".

He disputed a report that emerged over the weekend detailing a study by quantity surveyor Michael Byng who estimated that the cost of HS2 could balloon to more than £100bn, making it the most expensive railway in the world. Mr Grayling described the figure as "nonsense".

Commenting on the decision to spend on infrastructure amid the 1% cap on public sector pay, Mr Grayling said: "That's a very different issue because we are talking about capital investment over the next 15 years. We are not talking about current spending that the chancellor will decide on come the Budget."

The contracts to design and build areas of the high speed rail line have been split into three groups: south, central and north.

Carillion, which last week issued a profit warning and announced the immediate departure of its chief executive, has won two "lots" within the central area. Its share price rose by 7.7% to 60.5p on Monday but it has fallen by more than 76% over the last 12 months.

This includes one of the most controversial and complex areas of the route that runs between the Chiltern tunnels and Brackley.

Carillion, which is part of a consortium with three other companies to design and build the two lots, announced on Monday that it had appointed accountancy firm EY to support a strategic review of the business.

'Important step'

The decision over its route through the North of England has been delayed for several years due to a series of disagreements, the most controversial of which has been which route it should take through Sheffield.

The government's preferred plan for the route through Yorkshire would mean bulldozing the newly built Shimmer estate in Mexborough.

Analysis: Richard Westcott, Transport Correspondent

Image copyright Getty Images

The government says HS2 is "on time" but they're clearly not talking about the route for the second phase, which was first promised in around 2014.

I remember flying a drone over a farm in Cheshire four years ago, filming the proposed route at the time.

The farmer has been waiting ever since then to find out if he'll lose his business.

He got in touch with me last year saying, "obviously we know nothing more today than we did when you were with us nearly 30 months ago, as the decision for HS2 Phase 2b has been put off yet again".

Anyone affected by the line now gets a year or two to put their case together and present it to a special committee of MPs who'll go through thousands of fears and objections before recommending any changes to the final route or the way it's designed.

When you talk to people adversely affected by HS2 they all say the same thing. Their lives go into limbo, often for years, just waiting for answers.

Set to open in 2026

Parliament granted powers to build the first phase of the line between London and Birmingham in February.

Preparatory work has begun and major construction work is due to start in 2018-19. It is due to open in December 2026.

A Bill to deliver Phase 2a from the West Midlands to Crewe will be published by Mr Grayling later on Monday. Services on this section are due to begin in 2027.

Phase 2b from Crewe to Manchester, and Birmingham to the East Midlands and Leeds, is due to open in 2033.

The companies who have won the contracts to design and build the first phase of HS2 are:

Area South

Euston tunnels and approaches - SCS joint venture: Costain (UK), Skanska Construction UK (Sweden) and STRABAG (Austria)

Northolt tunnels - SCS JV

Area Central

Chiltern tunnels and Colne Valley Viaduct - Align joint venture: Sir Robert McAlpine (UK), Bouygues Travaux Publics (France) and VolkerFitzpatrick (UK)

North Portal Chiltern tunnels to Brackley - CEK joint venture: Carillion Construction Ltd (UK), Eiffage Genie Civil SA (France), Kier Infrastructure and Overseas (UK)

Brackley to south portal of Long Itchington Wood Green tunnel - CEK JV

Area North