Theresa May told EU leaders "I think I'd better leave now" after they met a short speech about her Brexit ambitions with silence.
Shortly before leaving the summit in Brussels, the Prime Minister made a brief presentation to the 27 leaders on the UK's Brexit position, highlighting her desire to guarantee the rights of migrants.
According to one of the European leader's aides, there was an awkward pause as they waited for her to leave the room before she said: "I think I'd better leave now".
The source told The Times: "She was very polite but it was a bit embarrassing. It was a difficult moment for diplomatic etiquette."
In her speech May also said that the Government plans to push ahead with triggering Article 50, which will formally open two years of Brexit talks, in March despite a Supreme Court case.
European leaders are refusing to enter into discussions about Brexit with Britain until Article 50 is triggered. Earlier this year May told Angela Merkel, the German Chancellor, about her desire to secure an early deal on migrants' rights but was rebuffed.
Enda Kenny, the Irish Taoiseach, said: "She would like to have the question of UK citizens living in Europe and European citizens living in the UK dealt with in the early part of discussions that take."
He disclosed that she also said the Government has "good grounds to appeal" against a High Court ruling which said MPs should be given a vote. He added: "There wasn't any response to either of those comments."
After May left EU leaders spent just 20 minutes discussing the issue of Brexit at a late night meeting. Donald Tusk, president of the European council, described it as a "short informal meeting".
First published in the Telegraph as Revealed: How Theresa May's fight for British expat rights was met with silence from EU leaders