Lord Malloch-Brown, the junior minister who ruffled feathers by proclaiming himself the “wise eminence” at the Foreign Office, will now take the Prime Minister’s seat at a UN summit of world leaders, diplomats say.

The former UN second-in-command, who was elevated to a peerage and given a seat in the Cabinet by Gordon Brown, will represent Britain at a Security Council summit of heads of state and government in New York on September 25 alongside such leaders as President Sarkozy of France and possibly President Bush.

The plan has provoked grumbles at UN headquarters that Britain is breaking diplomatic protocol by sending a junior minister to such a high-level event. Mr Brown does not intend to travel to New York for the annual UN session this year because it clashes with the Labour Party conference. Sources say Mr Brown jokingly explained to Ban Ki Moon, the UN Secretary-General, when he visited UN headquarters this month that he could not risk missing the Labour Party conference because then he might not be Prime Minister next year.

Britain’s diplomatic snub is compounded by David Miliband, the Foreign Secretary, who also wants to attend some of the party conference and will not travel to the UN until the evening of September 26, halfway through the annual “ministers’ week”. The slight will be all the more obvious because Mr Brown’s predecessor, Tony Blair, will be at UN headquarters in his new role as envoy of the Middle East Quartet. The choice of Lord Malloch-Brown to attend the Security Council summit on peace and security in Africa has raised eyebrows, particularly among the French delegation, which is organising the event.

Lord Malloch-Brown served as the UN’s Deputy Secretary-General until the end of last year, before becoming vice-chairman of the billionaire George Soros’s hedge fund. On taking office, Mr Brown gave Lord Malloch-Brown a seat in the House of Lords so that he could name him Foreign Office Minister for Africa, Asia and the UN, with the right to attend Cabinet. The Foreign Office has, however, tried to muzzle him since he questioned Britain’s relationship with the United States and suggested that he would play elder statesman to the younger Mr Miliband, his boss.

He told The Daily Telegraph: “It’s fine for me to be, for the first time in my life, the older figure, the wise eminence behind the young Foreign Secretary.” Lord Malloch-Brown has made no secret of his disdain for American neoconservatives, raising questions over whether Mr Bush will attend the Security Council summit if Britain is represented by him.

French diplomats say that they are still gathering responses to their invitations, but that President Kufuor of Ghana had already signalled that he will attend. British officials explain that Lord Malloch-Brown will be the head of the British delegation to the annual UN session until Mr Miliband arrives, outranking his Foreign Office colleague Kim Howells; Douglas Alexander, the International Development Secretary; and Hilary Benn, the Environment Secretary.

Ironically, Lord Malloch-Brown, who joined the Labour Party to take up his ministerial post, will not attend the Labour Party conference, even though he did so last year while still serving at the UN.

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