Reports yesterday said the SNP wants to use the anniversary of Scotland's most famous victory over the English, on June 24, 1314, to tap into nationalist fervour.
It also coincides with the 2014 Commonwealth Games and Ryder Cup at Gleneagles.
The SNP last night refused to confirm or deny the speculation, simply saying it would be held in the second half of the current parliament.
A referendum bill is likely to be introduced to Holyrood towards the end of this year or the start of 2013.
Reports quoted senior SNP figures as claiming "nothing was set in stone" but "autumn 2014 is shaping up to be the target date for the referendum".
Other party sources claimed Labour and the LibDems "look set to fall into a trap of their own making by campaigning with the Tories against any more powers for Scotland".
Despite noises on a united front to preserve the Union, the main parties are divided on what to offer as an alternative.
New Scottish Labour leader Johann Lamont has indicated she is opposed to sharing a campaign with the Tories. She said: "The SNP needs to act maturely and set the referendum date once and for all to end this unnecessary uncertainty. They should start acting in the interests of Scotland – not just themselves."
Willie Rennie, of the Liberal Democrats, said: "The SNP should be answering questions on the cost of splitting Scotland from the UK."
An SNP spokeswoman said: "We will do exactly as we said we would in the election – hold the referendum in the second half of this parliament, based on the resounding mandate we received from the people of Scotland."