A senior Labour figure has voiced support for the HS2 north-south rail link - just a day after the party's shadow Treasury team raised the prospect of scrapping it.
Maria Eagle, shadow transport secretary, said the line would reduce journey times and tackle overcrowding.
From the off, the three main party leaders have backed the project.
But on Tuesday, first Ed Balls then Rachel Reeves said a Labour government would review it after the election.
The shadow treasury ministers said Labour would reassess whether the new line was the "best way to spend £50bn".
'Get a grip'
Ms Eagle told activists at the party's conference Mr Balls had "rightly said there can be no blank cheque for any government project."
But she added: "Let's free up space for new commuter services by moving the growth in longer journeys on to a new north-south rail line - reducing journey times, getting more freight off our roads."
And she departed from a draft version of her speech, adding in the line: "That's why we support high speed two."
Affirming her backing for the project she told the party conference in Brighton: "I say to Cameron, get a grip on this project... on its budget, and get it back in on track."
Full steam ahead
On Tuesday the Labour leader of Manchester City Council criticised his party for raising doubts about its viability, accusing Mr Balls of a "cheap shot".
Sir Richard Leese - head of the Labour council since 1996 - said the high-speed line was "essential" to prevent the North and Midlands "slowly grinding to a halt".
"There are better ways for the shadow chancellor to demonstrate fiscal responsibility than take a cheap shot at HS2," he added.
BBC transport correspondent Richard Westcott said Labour would not commit to cancelling HS2 before the election, but would review it if they won.
He said Labour would look at whether it was the best way to spend £50bn, or whether they should look at other options, like different routes or big improvements to existing lines.
The project's first phase would see 225mph trains running on a new line to be built between London and the West Midlands by 2026. A second phase would see the line extended further north, with branches to Leeds and Manchester by 2033.
The estimated cost of the plan has risen in the past few months from £34.2bn to £42.6bn - plus £7.5bn for rolling stock - and some senior Labour figures such as Lord Mandelson and Alistair Darling now oppose the project.
HS2 has had the backing of all three main party leaders since its conception - despite strong opposition among some backbench MPs.
Mr Balls said in his conference speech: "David Cameron and George Osborne have made clear they will go full steam ahead with this project - no matter how much the costs spiral up and up. They seem willing to put their own pride and vanity above best value for money for the taxpayer."
Mr Balls added: "Labour will not take this irresponsible approach. So let me be clear, in tough times - when there is less money around and a big deficit to get down - there will be no blank cheque from me as a Labour chancellor for this project or for any project.
Construction on the London-West Midlands phase is expected to begin around 2017, once Parliament has approved the necessary powers - probably in 2015.
The onward legs to Manchester and Leeds could start being built in the middle of the next decade, with the line open by 2032-33.