Conservative and Liberal Democrat negotiating teams will meet again within the next 24 hours following more than five and a half hours of discussions in Whitehall.
Shadow foreign secretary William Hague emerged from the Cabinet Office to say that they would be briefing their respective leaders on what he described as "very positive and productive" negotiations on forming a possible power-sharing deal.
As the meeting broke up Conservative sources disclosed that David Cameron had spoken again by telephone to Nick Clegg following their 70 minute face-to-face talks last night in Whitehall.
Mr Clegg earlier spoke to Gordon Brown by phone, at the request of the Prime Minister, in a conversation which the Lib Dems again characterised as "amicable".
A spokesman for the Lib Dem leader indicated that Mr Brown's overture would not deflect Mr Clegg from pursuing his strategy of talking to the Tories first on a possible solution to the impasse caused by Thursday's General Election.