GORDON BROWN suffered another devastating blow last night after his work and pensions secretary quit and told him to stand down to save the Labour Party.<br /><br />James Purnell, a rising star and a leading Blairite, became the third cabinet minister to leave Brown&rsquo;s chaotic government this week and the first to openly call for Brown to resign. The dramatic development means that Brown is now only just clinging on to power, with some in Westminster convinced he may soon be forced out.<br /><br />The news comes as polls closed last night for European and local government elections, the last test of opinion ahead of a general election that must come within a year.<br /><br />In a letter to Brown, Purnell wrote: &ldquo;I now believe your continued leadership makes a Conservative victory more not less likely.&rdquo; Purnell added that he did not want to become leader of the party and was not acting in tandem with other MPs.<br /><br />Yet his call for Brown to step down comes just hours after backbench Labour MPs had begun circulating a letter calling on Brown to resign, with the number of signatories said to be growing by the hour.<br /><br />Purnell was seen as a talented and capable minister who rose swiftly through the ministerial ranks after working for former Prime Minister Tony Blair in Number 10.<br /><br />His resignation is far more damaging and unexpected than that of communities secretary Hazel Blears and home secretary Jacqui Smith earlier this week. Conservative leader David Cameron said the government was &ldquo;falling apart in front of our eyes&rdquo;.<br /><br />Brown said he was &ldquo;disappointed&rdquo; in Purnell&rsquo;s decision but would not quit. He said he would continue to work to steer the country out of recession. Yet Purnell&rsquo;s departure throws Downing Street into turmoil and may give Brown&rsquo;s critics the courage to make a final strike against his leadership.<br /><br />However, business secretary Peter Mandelson called for calm, saying plotting or an early election would only &ldquo;make things worse for the Labour Party&rdquo;.<br /><br />The move makes it very difficult for Brown to carry out the sweeping reshuffle he had planned. The Prime Minister had wanted to replace his former long-time ally chancellor Alistair Darling with schools minister Ed Balls.<br /><br />But sources close to Darling say he would prefer to go to the backbenches rather than leave the Treasury. Observers say in light of this week&rsquo;s damaging resignations it would be difficult for Brown to remove Darling against his will without triggering further devastating resignations and all-out war. The Labour Party lags more than 20 points behind the Tories and polls put it coming as low as fourth place in the European elections behind UKIP.