Senior government sources say the prime minister is poised to reverse his opposition to a referendum on the EU constitution.

In what could be one of his biggest policy U-turns, Tony Blair is examining plans to offer a nationwide vote on the outcome of the June talks.

Options under consideration, according to the Times, include a simple Yes/No vote on the constitution, a wider poll on UK membership of the EU, a manifesto committment to ratify the constitution or an election pledge to hold an EU referendum if Labour is returned to government.