Records revealed an encounter was arranged under the premise that Ms Natalia Veselnitskaya would share damaging information about Mrs Clinton, Mr Trump's Democratic party rival for the White House. Photo: BBC News

Rinat Akhmetshin, now a lobbyist, told AP news agency he was present at the encounter in Trump Tower.

Donald Trump Jr was promised damaging material on Hillary Clinton at the meeting, his emails show.

Mr Trump Jr has only previously acknowledged that a Russian lawyer, Natalia Veselnitskaya, was present.

The president's eldest son has played down the 9 June 2016 meeting since it was reported this week.

But a congressional panel investigating claims that Russia meddled in last year's US election, in a bid to help Donald Trump, has asked the president's son to publicly testify.

Emails show Mr Trump Jr, together with the president's son-in-law, Jared Kushner, and campaign chairman Paul Manafort, met Russian lawyer Natalia Veselnitskaya, who had reported ties to the Russian government, on 9 June 2016.

The records revealed the encounter was arranged under the premise that Ms Veselnitskaya would share damaging information about Mrs Clinton, Mr Trump's Democratic party rival for the White House.

Mr Trump Jr said it later became apparent that Ms Veselnitskaya wanted to discuss a suspended programme for Americans to adopt Russian children.

Since he was elected, President Trump has been dogged by allegations that Russia tried to sabotage Mrs Clinton's campaign to help him win.

He has rejected any knowledge of this and Russia has also repeatedly denied interfering.

During a news conference in Paris, Mr Trump defended his son, saying he was merely attempting to collect opposition research and that "most people would have taken that meeting".

"Nothing happened from the meeting. Zero happened," Mr Trump insisted.