Voters would reject the European constitution by a margin of two to one, according to the first poll to use the question the Government has chosen to put to the country. A survey conducted since the wording was published on Wednesday suggests that 45 per cent of the public would vote against the constitution, with only 24 per cent in favour. Tony Blair has staked his reputation on winning the referendum, which is expected next spring if Labour wins the general election.The results of The Telegraph's YouGov poll show that he faces an enormous challenge in trying to turn around public opinion. But they also indicate that a large part of the electorate is open to persuasion. Twenty five per cent of respondents said they did not know how they would vote if they were forced to take a decision tomorrow. Only 51 per cent said they had made up their mind about the constitution, which was agreed by European Union leaders last summer. Others would make a final decision nearer the time. Michael Ancram, the Conservative foreign affairs spokesman, said his party was right to oppose the treaty setting up the constitution. "This underlines the very real and deserved mistrust of the British people for this attempt to punch them into a European super-state. "We must continue to make the case against the constitution to ensure the British people firmly consign it to the grave."