IT’S been labelled “treason”, prompting one opposition congressman to file articles of impeachment against President Donald Trump less than 24 hours after emails confirmed his campaign sought help from the Russians to win the US election.

But experts predict a far less spectacular federal law could be the one used against him in the end.

Former US Attorney Joyce Vance says Donald Trump Jnr’s claim that a meeting he took with a Kremlin-linked lawyer on the promise of dirt on Hillary Clinton was “nothing” simply would not wash with the special investigator now probing Trump’s ties to Russia.

“It is far from nothing,” Ms Vance told the ABC’s Lateline.

“What’s wrong is not the effort to beat Hillary Clinton — that’s the central function of a campaign. What’s wrong here is the use of information from a foreign government,” she said, calling it “a bright line that can’t be crossed.”

“The allegations are very dangerous and we’re not done yet.”

Trump Jnr admitted he, his brother-in-law Jared Kushner and Trump campaign manager Paul Manafort met with Russian lawyer Natalia Veselnitskaya in 2016 amid promises of incriminating information about Mrs Clinton. Trump Jnr claims the 20-minute meeting — which he said turned out to be “a waste of time” — was simply “research”.

TANGLED WEB: All the Trump ties to Russia

While digging dirt on a political rival is not illegal in the US, obtaining a benefit with the help of a foreign government certainly is, Ms Vance said.

“American elections are national elections, they don’t have an international aspect, and so a foreign national can’t for instance contribute money to a campaign,” she said.

“It looks here like we have the Trump folks soliticing the Russians, in effect, for something of value — this “opposition research” — that they then go on and actually use. The allegations look serious. It looks like we have a conspiracy involving at least the three (men) that were in the room and perhaps more people.”

Overnight, a US congressman filed an article of impeachment against Donald Trump in a longshot bid to remove the president from office.

House Democrat Brad Sherman accuses Trump of obstructing investigations into Russian meddling in the 2016 presidential election, in part by firing former FBI director James Comey.

White House spokeswoman Sarah Huckabee Sanders said on Wednesday that Sherman’s resolution was “utterly and completely ridiculous”. Sherman’s effort in reality has little chance of success in the Republican-led House and he does not even have the backing of many fellow Democrats.

Former FBI director Robert Mueller has been tasked with investigating Trump ties to Russia.

Ms Vance said allegations of treason now being levelled at Trump would be difficult to prosecute, but Mueller’s team had other options.

“Treason is a little bit strong. It is a statute we use rarely in this country. There are a lot of other statutes that are a better fit.”

She said it was also highly unlikely Donald Trump himself did not know about the meeting his son took with the Russians.

“You also have Paul Manafort in the room, the then campaign manager, someone with decades of experience in campaigns,” she said.

“Manafort’s gut reaction, his first instinct, should have been to call the FBI. Had they called the FBI, had they called the US Attorney in Manhattan and said ‘We’re being approached by the Russians’, I suspect that what would have happened is the meeting would have gone forward with the FBI listening in and the Trump organisation wouldn’t be in the position that it’s in today.”

President Trump has called the scandal a “witch hunt”, claiming Russian President Vladimir Putin would have preferred Hillary Clinton in the Whie House anyway.

But Ms Vance believes the Kremlin has achieved some of its goals with Trump’s appointment.

“The Russians role here, the role of their intelligence service certainly, would be to disrupt the smooth functioning of the United States government on every level. They may have seen advantage in helping a less experienced, a little bit more volatile candidate take the White House. Of course it is now also in their interest to disrupt this presidency.”