The Government's HS2 high-speed rail plan was today backed by the House of Commons Transport Committee following its inquiry into the £34 billion project.
But the committee's approval came with a number of provisos including MPs urging supporters and opponents of the scheme to desist from name-calling and terms such as "Nimbys" and "Luddites".
The committee said there was a "good case" for HS2 which would feature 250mph, 1,100-passenger trains running from London to Birmingham and then on to north-east and north-west England and Scotland.
Bitterly opposed by some residents and councils, HS2 would run through picturesque Tory heartlands in its first phase from London to Birmingham, with the Government due to make a decision on the route before the end of this year.
The committee's report said: "We have pointed to a number of areas that we believe need to be addressed in the course of progressing HS2."
:: The provision of greater clarity on the (overall transport) policy context;
:: The assessment of alternatives;
:: The financial and economic case, with the committee saying it would be "unacceptable and counterproductive if investment in HS2 led to a diminution of investment in other parts of the rail network";
:: The environmental impacts;
:: Connections to Heathrow;
:: The justification for the particular route being proposed.
The report said: "We call on the Government to consider and to clarify these matters before it reaches its decision on HS2."
The MPs said: "Unlike policies for major roads and airports, this proposal has all-party support. It is not, however, universally supported by MPs or the public.
"We acknowledge the deeply held and often well-informed views on both sides of the debate."
The report went on: "What should have been a serious and factually based debate about how best to address the transport, economic and environmental challenges of HS2 has too often been reduced to name-calling and caricature.
"Luddites, Nimby and white elephants fought out a battle of 'jobs versus lawns'. We urge the Government to desist from disparaging opponents of HS2 as Nimbys and for both sides in the debate to show respect for each other and to focus on the facts."
The committee said the "absence of a transport strategy" made it harder to assess how HS2 related to other major transport schemes.
MPs said that, if the Government decided to go ahead with HS2, it should publish a summary of the financial case "including the assumptions which persuade ministers that the scheme will be affordable alongside sustained investment in the classic (rail) network".
The report continued: "The evidence we have received and our visit to France and Germany lead us to two conclusions about the potential of HS2 to stimulate national and regional growth.
"First, it is obvious that the economic impacts of high-speed rail (HSR) can vary and are not easily predicted. Only time will tell whether or not HS2 will, for example, help to rebalance the economy and reduce the north-south divide. Our judgment is that HS2 could indeed be the catalyst for these economic benefits."
The committee went on: "Our second conclusion is that, if HSR is to realise its full potential, the Government's plans for HS2 must be accompanied by complementary regional and local strategies for transport, housing, skills and employment."
The plan is for the London-Birmingham section of HS2 to open in 2026, with a phase two, Y-shaped extension taking in Manchester and Leeds being ready around 2032/33.
The report today said it was "disappointing that even basic information on the Y network, such as the number and location of stations, was not available during the public consultation or during our inquiry".
The MPs added: "We believe that there should be an urgent strategic appraisal of phase two before a final decision on phase one is taken."
The report also expressed the MPs' concerns about the speed of the trains on the route.
It said: "It may be that a high-speed line operating at less than 250mph may offer greater opportunities for noise and environmental impact mitigation, as well as an opportunity to follow existing transport corridors.
"We are concerned that the decision to build a 250mph line has prematurely ruled out other route options such as building HS2 alongside an existing motorway corridor such as the M40 or M1/M6."
On other suggested benefits of HS2, the MPs said: "It is disappointing that a major strategic scheme... is being designed and assessed to a large extent on the basis of the value of travel time savings, which are not universally accepted."
The report also said:
:: The Government needs to make clear how HS2 fits into its wider aviation strategy, looking again at the case for a direct link to Heathrow in phase one on the assumption that the HSR network will extend to Manchester and Leeds;
:: Better information should be provided to explain the Government's rationale for its proposals for London termini and linkages, which are the most expensive and complex elements of HS2;
:: Operating 18 trains per hour at speeds of more than 200mph were risk factors for which more technical information should be published. It is questionable whether the system proposed is being designed with sufficient margin for expansion;
:: Claims that HS2 would deliver substantial carbon-reduction benefits do not stand up to scrutiny;
:: The Government should engage with Network Rail to identify whether there are affordable options to enable more peak-time capacity to be provided for Milton Keynes and Northampton commuters before HS2 opens.
Dan Large, spokesman for the Campaign for High Speed Rail, said the report was "a victory for jobs in the North of England and the Midlands".
"They have told us for months that HS2 would never stand up to scrutiny, but the Transport Committee has decided otherwise."