Prime Minister Gordon Brown is under further pressure to step down as another minister has quit the Cabinet. Work and Pensions Secretary James Purnell has dramatically announced he is quitting parliament as polls closed in crunch elections. In a resignation letter released to several newspapers, Mr Purnell called on Mr Brown to step aside for the good of the Labour Party, saying that his continued leadership makes a Conservative victory more, not less, likely. The letter reads: "Dear Gordon, We both love the Labour Party. I have worked for it for twenty years and you for far longer. We know we owe it everything and it owes us nothing. "I owe it to our Party to say what I believe no matter how hard that may be. I now believe your continued leadership makes a Conservative victory more, not less likely. "That would be disastrous for our country. This moment calls for stronger regulation, an active state, better public services, an open democracy. It calls for a Government that measures itself by how it treats the poorest in society. Those are our values, not David Cameron's." The letter continues: "We therefore owe it to our country to give it a real choice. We need to show that we are prepared to fight to be a credible Government and have the courage to offer an alternative future. "I am therefore calling on you to stand aside to give our Party a fighting chance of winning. As such I am resigning from Government. "The Party was here long before us, and we want it to be here long after we have gone. We must do the right thing by it. "I am not seeking the leadership, nor acting with anyone else. My actions are my own considered view, nothing more. If the consensus is that you should continue, then I will support the Government loyally from the backbenches. But I do believe that this question now needs to be put. "Thank you for giving me the privilege of serving. Yours, Rt Hon James Purnell MP." Mr Purnell's departure follows the loss of four ministers from Mr Brown's Cabinet in the past three days, amid reports of backbenchers collecting signatures demanding his removal.