The "great Conservative fightback" starts now, David Cameron declared as he pledged to give voters a clear choice at the next General Election.The Conservative leader was addressing party activists for the first time at this year's Blackpool conference.He said: "This week we are going to mount the great Conservative fightback."It is going to be a fightback based on clear policies, based on a clear direction, and based on the clear choice that we will give people at the next General Election: more failure from Labour, more real change from the Conservative Party."Mr Cameron was speaking after a speech from Boris Johnson, the Tory candidate for London Mayor.Earlier he urged Gordon Brown to call a snap election saying: "We have got to have real change in our country."Mr Cameron said Labour had failed to deliver on public services and law and order after ten years in power.Asked if the Prime Minister needed to seek a mandate after replacing Tony Blair, Mr Cameron replied: "Yes, I think he does. I have always said we should have an early election. We are ready for it, we have the candidates ready in our marginal seats."We have a very clear and compelling message to people which is that we have got to have real change in our country."Latest polls showed Mr Cameron and his party both trailing badly behind Mr Brown and Labour but the Tory leader insisted: "This week we will be setting out a very compelling alternative - not just saying what we want to achieve but saying how we want to achieve it."Mr Cameron accepted that the party faced a "huge challenge" in the light of recent opinion poll findings. But he insisted he was more concerned about giving voters a clear alternative to the Government.© Independent Television News Limited 2007. All rights reserved.