( BBC ) - Opposition MPs have accused Gordon Brown of being indecisive and weak after he ruled out an autumn election.
Lib Dem leader Sir Menzies Campbell said the prime minister had a "crisis of confidence", while Shadow Chancellor George Osborne said he lost his nerve.
Opinion polls published by the Sunday Times and News of the World put the Tories ahead of Labour.
Mr Brown said he was delaying the vote to give people time to see how successful his policies had been.
The prime minister said he wanted a chance to show the country his "vision for change" and to develop his policies further.
He said an election could have been held based on "competency" in dealing with crises, but he wanted to develop housing, health and education.
Conservative leader David Cameron said Mr Brown had shown "great weakness and indecision", and had made a "humiliating retreat".
Mr Osborne said: "The Labour Party promised us at the last election that Tony Blair would serve the full term and then there would be an election.
"Well, Tony Blair's gone, the new guy's in charge, he's been there for a while now. He's deliberately stoked up speculation about an election and now he's gone and bottled it."
Sir Menzies said the prime minister's decision showed "a loss of nerve".
"He should have stated his intentions, clearly and unequivocally. The inevitable conclusion is that he's been acting in the interests of the Labour Party and not in the interests of the country," he said.
Lib Dem deputy leader Vince Cable said: "Gordon Brown's made a terrible mess of this really and undermined his credibility. And I think actually he may regret his decision to postpone the election."
But the government's assistant whip, Sadiq Khan, said Mr Brown had never intimated he was thinking of calling an election.
He said: "The prime minister has never publicly or privately said to anyone that it was his intention to hold a general election this autumn."
BBC political editor Nick Robinson suggested the main reason for not calling a snap election would be an unfavourable poll of marginal seats showing a swing to the Tories.
A poll published by Sunday's News of the World puts the Tories ahead by 6% in marginal seats, with the party overall at 44% against Labour's 38%.
Translated into a general election, it would mean a hung Parliament with Labour holding 306 seats and the Tories 246.
A poll carried out for the Sunday Times showed the Tories had taken a three-point lead.
Mr Brown revealed his decision not to call an election exclusively to the BBC's Andrew Marr on Saturday in Downing Street.
He said: "I'll not be calling an election. I have a vision for change in Britain and I want to show people how in government we're implementing it.
"Over the summer months we've had to deal with crises, we've had to deal with foot-and-mouth, with terrorism, with floods, we had financial crises.
"Yes, we could have had an election on competence and I hope people would have understood we have acted competently, but what I want to do is show people the vision we have for the future of this country in housing, health and education."