Mr Miliband spoke to the Russian foreign minister - a veteran not known for diplomatic niceties - to express British unease at events in Georgia. It seems Mr Lavrov didn't like being lectured by young Miliband.
Such was the repeated use of the "F word" according to one insider who has seen the transcript, it was difficult to draft a readable note of the conversation.
One unconfirmed report suggested that Mr Lavrov said: "Who are you to fuck lecture me?"
He also asked Mr Miliband in equally blunt terms whether he knew anything of Russia's history?
One Whitehall insider told: "It was effing this and effing that. It was not what you would call diplomatic language. It was rather shocking."
The Foreign Secretary had been putting forward Britain and Europe's objections to the actions of Russian which began when their tanks rolled into the breakaway region of South Ossetia last month. Mr Miliband has said that Europe should reassess its ties with Russia after its "aggressive" behaviour.
It is also understood that Mr Miliband was asked about Britain and America's invasion of Iraq, when Russian actions in Georgia were questioned, during the tense conversation that took place recently.
Sources at the Foreign Office confirmed there was swearing "but only from side". A spokesman for the Foreign Secretary said: "We do not discuss diplomatic conversations between foreign ministers."
Mr Lavrov, who was promoted under Vladimir Putin, has developed a reputation as the fearsome face of Russia's new aggressive foreign policy. When he held the position as Russia's man at the United Nations in New York he developed a reputation as fierce critic of other nations.
But Mr Miliband is unlikely to have experienced anything quite so bruising in his year as Foreign Secretary than being told some home truths by a grizzled veteran of the international scene. Even the slap down from MPs supporting Mr Brown after the Foreign Secretary's "leadership bid" article in July when he was accused of treachery, was not as bad.
Mr Lavrov has been highly critical of the way that the Russian move into Georgia has been portrayed by the West. He has criticised what he described as a "truly David and Goliath interpretation" of the conflict in which "the plucky republic of Georgia, with just a few million citizens, was attacked by its giant eastern neighbour".
After that sort of bawling out anything Gordon Brown and his allies can muster in response to Miliband's leadership ambitions is likely to be small beer.