The decision holds out the promise of much-needed design and consultancy work, expected to be worth up to £350m in fee income alone.

But the reaction from contractors was far more circumspect, as many feared the project start will be allowed to slip in the face of fierce local opposition and prolonged attacks on the cost effectiveness of the investment.

A spokesman for a national contractor said: “We of course welcome it, but the start date is set after the next election. A lot can happen between now and then as we have all seen over the years. The real heavy investment in construction seems like it is going to be a very long way off.”

Despite the caution about when contract work will materialise, the Civil Engineering Contractors Association called for contractors to be brought onto the project at the earliest stage.

CECA director of external affairs Alasdair Reisner said: “The announcement of the go-ahead for the first phase of High Speed 2 is both a phenomenal opportunity for industry, but also an enormous challenge.

“The delivery of HS2, both on time and to budget, will confirm the strengths of the UK infrastructure sector at home and abroad.

He added: “Nonetheless, the decisions that are being made now have the potential to have a huge impact on the delivery of the project. It would be hugely beneficial for those contractors who will be working on HS2 to be involved in the development of the project, even at this early stage.

The Association for Consultancy & Engineering chief executive Nelson Ogunshakin said: “Industry is pleased to see broad cross-party support for HS2.

“The transport select committee reported that no alternative to HS2 offered the increased rail capacity and there is general agreement that the project will pay economic dividends.

“We hope this will see challenges and public concerns resolved quickly and constructively so as to get the project underway without delays.”

One consultant told the Enquirer: “We have been waiting for this and it promises to really boost work at a time when there is little about. It’s a real lifeline for all of us, because not much else is going on in the UK.

He added: “Every major player in the industry is bidding for the consultancy work, which has already come out to tender.”

Government project promoter High Speed 2 Ltd plans to select a framework of firms this year to cover architectural and engineering services, urban planning and landscape engineering, technical testing and analysis services.

Professional fees for the front end of the project have been estimated to cost anywhere from £250m to £350m.

Chair of the Institution of Civil Engineers (ICE) HS2 Expert Panel, Steve Hayter, said: “Government’s willingness to explore different engineering options to minimise the impact on those communities affected must be welcomed.

“Tunnelling on this scale is a proven, effective engineering solution with many advantages. Engineers will now stand ready to do what they do best – overcoming any challenges and ensuring the project succeeds.”

Transport secretary Justine Greening revealed several new measures to mitigate the worst affects of the line, which will see journey times between London and Birmingham cut to just 49 minutes.

A new tunnel as the line passes through Ruislip in West London will remove all noise and visual impacts in that section of the route, and extended tunnelling  in the Chilterns will bring further benefits to that area.

The length of the line which is in tunnel or green tunnel has been increased by over 50%, to around 22.5 miles in nine individual sections.

In addition, around 56.5 miles of the 140 mile route will be partially or totally hidden in cuttings, and the amount on viaduct or embankment  has been substantially reduced.

This means that well over half of the route would be mitigated by a tunnel or cutting.

The Government also confirmed plans for a London link between HS1 and HS2 to allow passengers from Europe non-stop travel to the North.

The decision will also see huge investment in London’s Euston Station and a new station development at Old Oak Common in Hammersmith and Fulham.