Democratic US presidential candidate Joe Biden said Wednesday for the first time that President Donald Trump must be impeached for abusing the powers of his office to help his own re-election.

Mr Biden made the remarks as part of a blistering 25-minute campaign speech in New Hampshire.

He said Mr Trump is “shooting holes in the Constitution” by asking foreign powers to interfere in the 2020 election and then refusing to co-operate with a resulting House of Representatives impeachment inquiry.

“This is a president who has decided this nation doesn’t have the tools, the power, the political will” to punish bad behaviour, Mr Biden said.

“He’s not just testing us. He’s laughing at us.”

Mr Trump quickly shot back in a tweet that it was “so pathetic” to see Mr Biden calling for his impeachment.

The president maintained that he had done nothing wrong.

Mr Trump, in a July phone call to Ukraine’s leader, had asked for “a favour” of investigating Mr Biden and his son Hunter.

Democrats in the House of Representatives have begun impeachment proceedings against Mr Trump based on a rough transcript of the July 25 telephone call.

Mr Trump maintains his unfounded assertions that Mr Biden, as vice president, used his office to protect his son from corruption investigations in Ukraine.

Mr Biden on Wednesday again called those theories “lies” and said Mr Trump was peddling them because he fears facing Mr Biden in a general election.

“We’re not going to let Donald Trump pick the Democratic nominee for president,” Mr Biden said.

“I’m not going to let him get away with it. He’s picked a fight with the wrong guy.”