Speaking at a Scots reception at his party's annual conference in Birmingham, Mr Cameron said he was ready to fight the referendum should the SNP "ever call one" but admitted that such a move didn't look likely at the moment.
"I will be on that campaign if they ever have the courage to call that referendum on the future of the United Kingdom but it doesn't look like they do right now does it,” he said.
The SNP had pledged to hold a referendum as part of their programme following the 2007 elections but confirmed last month the referendum was been put on hold because opposition parties made it very clear that they would to block the bill.
Mr Cameron also said he was committed to increasing the Conservative party's standing across the border. Scotland only returned one Conservative MP in May's election and the party failed to increase its overall vote share.
However, the party looks set to perform a major policy U-turn and go into the forthcoming Scottish election offering to form a coalition to get into government at Holyrood. This is quite a U-turn remembering that following the 2007 election, the Conservatives ruled out a deal with the SNP because they could not support Alex Salmond's plans for an independence referendum...