A former White House ethics lawyer has called Donald Trump's firing of FBI Director James Comey - who was heading an investigation into alleged Russian ties to the 2016 election - a scandal "worse than Watergate."

Mr Trump fired writing in the letter used to dismiss Mr Comey, said that the FBI Director had eroded public confidence and trust in the bureau. Mr Comey was set to serve the usual 10 year term, having only been confirmed to the position in 2013.

Richard Painter, who worked for President George W. Bush, told Rolling Stone that the 1972 scandal involving a break-in at the Democratic National Committee offices in the Watergate office complex and the subsequent attempted cover-up by President Richard Nixon was just a "third-rate burglary" compared to what Mr Trump is doing.

"It was purely domestic in nature. This situation involves Russian espionage, and we've got to find out who is collaborating," Mr Painter said.

Mr Painter was wary of Mr Trump saying he followed the recommendation of Attorney General Jeff Sessions and the Department of Justice. Deputy Attorney General Rod Rosenstein. Mr Rodenstein wrote a memo to Mr Sessions regarding Mr Comey's "wrong" handling of an investigation into then-Secretary of State Hillary Clinton's use of a private email server to send classified information.

Mr Painter claimed that Mr Sessions "was also part of the contacts made by the Trump campaign with Russia. The attorney general lied about that to the Senate at his confirmation hearing".

There is no evidence that Mr Sessions had any Russian ties while he worked on Mr Trump's 2016 campaign, however he did recuse himself from the investigation into Russian interference with the election on the advice of DOJ lawyers.

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"It was an abuse of power," Mr Painter said, noting that the president does have the legal right to fire the FBI Director.

He drew comparisons to Mr Nixon firing then-special prosecutor Archibald Cox who was looking into the Watergate burglary and White House cover up. It prompted the resignations of Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus because they refused to fire Mr Cox themselves.

The difference between the two story lines is that Mr Nixon's attorney general was not party to the scandal unlike Mr Sessions, said Mr Painter.

Mr Painter called for the House Judiciary Committee to hold a hearing and begin the impeachment process.

Republicans, despite some critics of the president among the ranks, have been reluctant to set up an independent commission to take over the Russia investigation.