Donald Trump and the Republican party are using the prospect of impeachment to raise a record election war chest, firing up supporters and hauling in unprecedented amounts of money.

Republican officials said there had been a "groundswell" of support from the party's rank-and-file in the days after Democrats in Congress announced an impeachment inquiry into the president over the Ukraine scandal. It looks set to spur Mr Trump to an extraordinary total for the 2020 campaign, which could ultimately hit $2 billion.

In the 72 hours after Nancy Pelosi, the Democrat House speaker, announced the impeachment inquiry Mr Trump's re-election campaign took in $15 million, which his campaign manager Brad Parscale described as "amazing".

The more significant figure was that it included money from 50,000 new small donors, who were from all 50 states.

At one point Mr Trump sent out an email saying "I've done nothing wrong, trust me," asking for support for an "Impeachment Defense Task Force". Around $1 million arrived in the next three hours.

The impeachment inquiry was launched after a CIA whistle-blower raised the alarm about a July 25 telephone call between Mr Trump and Volodymyr Zelenskiy, the president of Ukraine.

Mr Trump is accused of pressuring Mr Zelenskiy to investigate Joe Biden, the Democrat front-runner, over business dealings his son Hunter had with an energy company in Ukraine. Both Bidens have denied any wrongdoing.