Remarks by the Queen, in which she appeared to mock Gordon Brown, were picked up by microphones after he seemed to get lost during a state banquet at Windsor Castle.
A witness suggested that the Prime Minister, known for his dislike of the formality that typifies royal events, simply walked the wrong way round the banqueting table at the event in honour of Nicolas Sarkozy and his wife, Carla.
Leaning across the table, the Queen laughed and said to Princess Anne: "The Prime Minister got lost." She added: "He disappeared the wrong way... at the crucial moment." The comments were picked up by the microphones placed on the banqueting table for the speeches.
One guest who witnessed the Prime Minister's apparent error said: "He thought he was supposed to be in the line for the greeting, but he should have been sitting down like the rest of us.
"When he discovered his mistake, he had to walk the long way round the table."
Downing Street brushed off the matter, blaming the Palace's staff for getting the protocol wrong. "He does what he is told on these state occasions," said the Prime Minister's official spokesman. "I don't think this is something that is troubling him very much."
The French President, who speaks little English, was sitting next to the Queen but seemed to be oblivious to the incident.
Downing Street aides refused to speculate on where Mr Brown had gone when he "got lost". A spokesman for the Palace said: "If anything happened, we're not aware of it." A mistake would have been easy to make. There were 160 guests in the vast banqueting hall, including 12 members of the Royal Family.