David Miliband said his relations with No 10 remained positive as he praised the "major contribution" of prime minister Gordon Brown to his efforts in Georgia.
The foreign secretary was responsible for a wave of media speculation about a potential leadership challenge last month after a Guardian article appeared to challenge Mr Brown's direction.
He denied such claims but refused to back Mr Brown publicly. Since then Russia's actions in Georgia have prompted an international crisis to distract him from the domestic political scene.
"There are no frosty relations at all within the government," the BBC quoted him as saying at a joint press conference with Georgian president Mikhail Sakkashvili in Tbilisi last night.
"I'm working closely with the prime minister on this issue. Just yesterday we were talking about the next steps - he's been making a major contribution at head of government level."
Mr Brown, who has been on holiday for the last three weeks but returns to work this week, issued a statement following the ceasefire announcement on August 12th calling for humanitarian aid.
Mr Miliband's comments came in response to a question about whether a cold war existed within the Labour party.
He added: "This is clearly an international crisis, which the whole of the important work of the Foreign Office is now focussed on, obviously, and the prime minister and I are working closely together on the issue."