Liberal Democrat Leader Nick Clegg said:

"Over the past four days we have been working flat out to deliver an agreement that can provide stable government that can last.

"The talks with the Conservatives have been very constructive and I am grateful to David Cameron and his team for the effort they have put in. But so far we have been unable to agree a comprehensive partnership agreement for a full Parliament.

"We need a government that lasts which is why we believe, in the light of the state of talks with the Conservative Party, the only responsible thing to do is to open discussions with the Labour Party to secure a stable partnership agreement.

"We will of course continue our discussions with the Conservative Party to see if we can find a way to a full agreement.

"Gordon Brown has taken a difficult personal decision in the national interest.

"And I think without prejudice to the talks that will now happen between Labour and the Liberal Democrats, Gordon Brown's decision is an important element which could help ensure a smooth transition to the stable government that everyone deserves."