Israel's Foreign Ministry said yesterday that the country's ambassador to the UN made an "error of judgement" by chatting and being photographed with Marine Le Pen, leader of France's extreme right wing National Front, at a New York reception.

Ron Prosor, formerly Israel's ambassador to London, has explained that his presence at a lunch last week for Ms Le Pen – whose party has long been shunned by Israel as a matter of government policy – last week was a "mistake." But while he was also quoted in the Israeli daily Haaretz yesterday as saying that he left "immediately" when he realized his error, it has emerged that he did indeed stay long enough to have a conversation with the National Front leader which she later reportedly described as "warm". And Mr Prosor was filmed by a French TV crew shortly after leaving saying that he and Ms Le Pen had talked about "Europe and other topics" and that he had "very much enjoyed the conversation."

The Labour Knesset member Daniel Ben Simon said last night it was "outrageous" that the meeting had taken place and he would be asking the Foreign minister, Avigdor Lieberman, today whether Mr Prosor had been instructed to attend the function. "Are we now adopting a racist party?" he asked. "This is very, very serious."

The photograph of the meeting was published in French newspapers, including Le Monde, which recalled the infamous remark by Ms Le Pen's father Jean-Marie Le Pen, the National Front founder, that concentration camp gas chambers were a "point of detail of the history of the Second World War."

Yigal Palmor, spokesman for Israel's foreign ministry, said that Mr Prosor had arrived at the lunch under the misapprehension that it was being hosted by the French mission to the UN. "When he realized who was there he tried to sneak away without causing a spectacle but he was spotted by the lady and engaged in conversation." Mr Prosor had been anxious to avoid making a scene and had stayed for about 20 minutes, he said.

While the Congolese Ambassador was said to have also mistaken the nature of the occasion, he reportedly turned on his heel as soon as he realised what it was and was overheard loudly upbraiding his secretary on the telephone for sending him to the lunch.

Mr Palmor admitted it was a "faux pas" and "an error of judgment", and was emphatic yesterday that there was no change in Israel's long-standing policy of "non-contact" with Ms Le Pen's party, which had failed to disavow its "legacy of xenophobia and racism."