David Miliband has clashed with Sri Lanka's defence secretary over the safety of civilians in rebel-held areas.
The argument is beleieved to have taken place as the Foreign Secretary was briefed by Gotabaya Rajapaksa on the situation during an official visit to the country this week.
The Foreign Office denied that discussions, which also involved Britain's High Commissioner to Sri Lanka Peter Hayes, had ended in a 'stand up row'.
But one official who had been at the meeting said there had been a 'free and frank and clear exchange of views' - diplomatic speak for a spat.
According to a report posted on the official Sri Lankan Defence Ministry website, the meeting became tetchy when the Foreign Secretary said that civilians were being caught up in artillery raids.
The report said that Mr Miliband 'interrupted' Gotabaya Rajapaksa, the Defence Secretary, as he was describing how the army had rescued 200,000 people from the tiny strip of north-eastern coastline where it has pinned down the Tigers.
Mr Miliband said the UK had 'credible information' of casualties.However, he was accused of being 'duped' by a propaganda campaign orchestrated by Tamil Tigers, who are officially known as the Liberation Tigers of Tamil Eelam (LTTE).
'Apparently annoyed, the Defence Secretary said anyone who knew the LTTE would not believe that any reliable information would emanate from that area under its jackboot,' the online account said.
It went on: 'The Defence Secretary said it was up to the British delegation to decide whether it should believe what a terrorist group said or what a responsible officer of a legitimate Government told them.'
'The choice is yours,' he was quoted as saying. It is possible that the Sri Lankan Government, which is determined to ignore international pressure - particularly from its old colonial ruler, has deliberately overplayed its version of the meeting to curry favour with its domestic audience.
As troops have pushed the rebels into an ever- shrinking area of less than four square miles, both sides have accused the other of endangering 50,000 non-combatants there.
Rights groups say the rebels are holding many to use as human shields. But they also accuse the Government of indiscriminate shelling to try and end the 26-year war. Both sides deny the allegations.
Mr Miliband had been in Sri Lanka with his French counterpart Bernard Kouchner to urge the Government to call a ceasefire to allow humanitarian aid to tens of thousands of civilians trapped on the front line.
Their mission ultimately failed and the reports of a diplomatic dispute will further damage Britain's credibility with Sri Lanka, .
The Defence Secretary apparently told Mr Miliband: 'The only person who could stop this war is...the President of Sri Lanka.'
He is also said to have mocked a demand from Mr Kouchner that the United Nations be given access to the civilians trapped with the Tigers.
A Foreign Office spokesman said tonight: 'We do not recognise this account of the meeting.
'But what is certainly true is that the Foreign Secretary set out clearly the importance of a ceasefire and humanitarian assistance with all the key members of the Government of Sri Lanka that he met.'
Source : BBC