US President Donald Trump has defended his eldest son over a meeting with a Russian lawyer last year, declaring on Twitter that he is “open, transparent and innocent”.

The comments came a day after Donald Trump Jr revealed his eagerness to hear damaging information about Hillary Clinton from the Russian government in a meeting with the lawyer from Moscow during the presidential campaign.

Defending his son’s conduct, the president again dismissed the ongoing Russia investigation as the “greatest Witch Hunt in political history”.

Mr Trump responded after Mr Trump Jr disclosed a series of emails on Tuesday that marked the clearest sign to date that Mr Trump’s campaign was willing to consider election help from a long-time US adversary.

The email exchange posted to Twitter by Mr Trump Jr showed him conversing with a music publicist who wanted him to meet with a “Russian government attorney” who supposedly had dirt on Mrs Clinton as “part of Russia and its government’s support for Mr Trump”.

The messages reveal that Mr Trump Jr was told the Russian government had information that could “incriminate” Mrs Clinton and her dealings with Russia.

Kremlin-linked lawyer Natalia Veselnitskaya speaks to journalists in Moscow (Alexander Zemlianichenko/AP)
Kremlin-linked lawyer Natalia Veselnitskaya speaks to journalists in Moscow (Alexander Zemlianichenko/AP)

Meanwhile, Mr Trump defended his eldest son on Twitter, writing that Donald Trump Jr was “open, transparent and innocent”.

He again called the Russia investigation the “greatest Witch Hunt in political history”.

Mr Trump’s lawyer also defended the president’s son, saying he did not violate any laws in his meeting with the Russian lawyer.

Jay Sekulow said Mr Trump was not aware of Donald Trump Jr’s June 2016 meeting and did not find out about his son’s email exchange until “very recently”.

“I love it,” Mr Trump Jr said in one email response.

Donald Trump Jr said there had been "nothing to tell" his father after the meeting (Richard Drew/AP)
Donald Trump Jr said there had been “nothing to tell” his father after the meeting (Richard Drew/AP)

The president’s lawyer, Jay Sekulow, said in an interview with NBC’s Today that Mr Trump Jr did not violate any laws by accepting the meeting.

He said the president had not been aware of Mr Trump Jr’s June 2016 meeting and did not find out about his son’s email exchange until “very recently”.

Mr Sekulow said the president was not being investigated by former FBI director Robert Mueller, the special counsel investigating the Trump campaign and its interaction with Russia during the election.

“I would know a little bit about it. I’m one of the lawyers,” Mr Sekulow told ABC’s Good Morning America.

As the emails reverberated across the political world, Mr Trump Jr defended his actions in an interview with Fox News, blaming the decision to take the meeting on the “million miles per hour” pace of a presidential campaign and his suspicion that the lawyer might have information about “under-reported” scandals involving Mrs Clinton.

He said the meeting “really went nowhere” and that he never told his father about it because there was “nothing to tell”.

“In retrospect I probably would have done things a little differently,” Mr Trump Jr said.