PRIME Minister Julia Gillard says Wayne Swan was making a "common sense point" when he claimed the US Republican Party had been hijacked by "cranks and crazies".

During a speech in Sydney on the global economy, the Treasurer said the same people had taken over a part of the Republican Party and were "the biggest threat to the world's biggest economy".

He was highly critical of the Tea Party wing of the Republican Party and accused it of holding the US national interest hostage during the debt ceiling crisis last year.

"There can be few things more alarming in public policy than a political movement which was genuinely prepared to see the US Government default on its obligations in order to score a political point," Mr Swan said.

Mr Swan's controversial statements drew inevitable comparisons with former prime minister John Howard, who early in 2007 said a Democratic Party win in that year's US election would be celebrated by terrorists.

That comment was rebuked by then Opposition Leader Kevin Rudd, who attempted to censure Mr Howard in the Parliament and claimed it would affect Australia's relationship with the US.

But far from rebuking Mr Swan, Ms Gillard said his comments were "appropriate".

"The strength of the American economy matters to the global economy," Ms Gillard said. "What happens in the US economy matters to the world economy and it matters to us. Risks to the US economy, therefore, matter for the global economy and ... for us.

"Wayne Swan was making that very common sense point today."

In a press conference after the speech he accused Opposition Leader Tony Abbott and the Coalition of adopting Tea Party tactics in Australian politics.

Mr Abbott was highly critical of the speech when fronting the media in Sydney.