Legislation to pave the way for the construction of the HS2 High Speed rail link is not likely to complete its passage through Parliament before next year's general election, Transport Secretary Patrick McLoughlin has indicated.
Failure to get the HS2 bill onto the statute book by the time of the May 2015 poll could make it a contentious election issue between the parties, particularly in constituencies along the route of the proposed line.
Questions were asked about Labour's commitment after shadow chancellor Ed Balls said there would be "no blank cheque" for HS2, which will link London to Birmingham before being extended further north.
Meanwhile, Mr McLoughlin suggested that voters will not get a chance to pass their verdict in a general election on the equally contentious issue of new airport capacity for the south-east, telling The Spectator magazine that he expects construction work to start before the poll expected in 2020.
David Cameron took the issue out of the political arena for the 2015 contest by asking Sir Howard Davies to conduct an independent inquiry, to report after the election.
The Davies Commission's interim report in December found there was a need for one new runway by 2030 and identified Heathrow and Gatwick as candidates for further study, with an announcement later this year on whether a "Boris Island" proposal in the Thames Estuary will join them on the shortlist.
Asked whether he expects building work to begin between the publication of Davies' final report and the 2020 election, Mr McLoughlin replied: "Sitting here now, that would be what I would hope."
On the issue of whether the High Speed Bill will gain Royal Assent by the time of the next election, the Transport Secretary said: 'I think one has to accept that perhaps through all its stages within the next 12 months is slightly ambitious."
The Spectator reported that Mr McLoughlin said the Bill - which was published last November but is yet to receive its second reading in the House of Commons - will have "started its parliamentary progress" within that time-span, but when asked if it would complete it by the election, he replied: "No."
A Department for Transport spokesman said: "We are confident that we are on track to have spades in the ground in 2017 as planned. A hybrid Bill will continue its passage through Parliament once it has started even after a general election.
"What matters is construction and completion and we are on course to deliver."