Detailed plans for a new high speed rail line linking London and Birmingham will be published in March, the Government has pledged.
But Conservatives accused Labour of delaying a decision until after the next election - following rumours that a poll could be held on March 25.
Transport Secretary Lord Adonis confirmed that a report giving details of the new line would not be published immediately, even though it is due to be completed before Christmas.
An inquiry set up by the Government will make detailed recommendations about the route a new line should take, but it will not be published until it has received “detailed scrutiny” from Ministers.
This is partly because the findings could potentially have a dramatic effect on property prices, according to the Government. Legal advisors in the Department for Transport have warned Lord Adonis that it should only be published once Ministers are able to say whether they accept its findings or not.
But it could delay publication until after a general election - after Westminster was awash with rumours last week that Gordon Brown planned to go to the country at the end of March.
Ministers will be barred from making announcements in the weeks leading up to the election.
Theresa Villiers, the Conservative Shadow Transport Secretary, said: “Labour have been struggling to keep up on high speed rail since 2008, when the Conservatives made their time-tabled and costed commitment to deliver a line connecting London, Birmingham, Manchester and Leeds with continental Europe through the Channel Tunnel.
“Now Lord Adonis has admitted that his aspirations for a line to the West Midlands won’t even be announced until Spring next year – potentially after the date for a March election.
“Labour are dragging their feet on High Speed rail. Only a Conservative Government can guarantee to bring high speed rail to the north.”
Although the Government originally committed itself only to building a line between London and Birmingham - saying it would then consider extending it further - it has recently stressed its desire to build a full national network.
Lord Adonis said: “The potential for high speed rail to regenerate and reinvigorate is now a reality for people in Kent, but the size of Britain’s high speed network lags behind that of many of our European neighbours and doesn’t connect any of our major cities.
“This month I expect to receive a report which has the potential change all that. This will require careful study and scrutiny - which will begin with immediate effect - before we can announce how we plan to take high speed rail forward in the Spring.”
The report will be presented to Lord Adonis by High Speed Two, a company set up by the Government specifically to look at options for high speed rail.
It will present a selection of different options for Ministers to consider, although it will also include guidance on which it considers most appropriate.
The report is likely to make a clear recommendation on whether services should run directly to Birmingham International Airport, and whether Birmingham City Centre needs a new station to cater for high speed trains.
Although Birmingham’s business community and the city council are firmly behind high speed rail, West Coast Main Line operators Virgin Trains told a recent Commons inquiry that there was little advantage in running services between London and Birmingham because journey times of less than an hour were possible on existing tracks.
High speed trains made sense over longer distances, such as between London and Scotland, Virgin said.