DONALD TRUMP has accused his predecessor Barack Obama of wire-tapping his phone a month before he was elected.

President Trump tweeted early on Saturday: "Terrible! Just found out that Obama had my "wires tapped" in Trump Tower just before the victory. Nothing found. This is McCarthyism!"

He went on to say that a court had earlier denied a wiretap request.

Trump has given no details to back up the claim – or suggested which court order he was referring to.

His tweets followed allegations made by conservative radio host Mark Levin, which were later picked up by Breitbart News, the website founded by Steve Bannon, now Trump's chief strategist.

Levin said there should be a congressional investigation into what he called President Barack Obama's "police state" tactics in his last months in office to undermine Trump's election campaign.

Breitbart summarises Levin's accusations, which say that "the Obama administration sought, and eventually obtained, authorisation to eavesdrop on the Trump campaign; continued monitoring the Trump team even when no evidence of wrongdoing was found; then relaxed the NSA (National Security Agency) rules to allow evidence to be shared widely within the government".

Media reports in the past few weeks have suggested the FBI had sought a warrant from the Foreign Intelligence Surveillance Court (Fisa) last summer in order to monitor members of the Trump team suspected of irregular contacts with Russian officials.

The warrant was first turned down but then approved in October, according to the media reports. There has been no official confirmation and it is also not clear if this evolved into a full investigation.

There has been no comment yet from Obama. But Ben Rhodes, who was his foreign policy adviser and speechwriter, responded: "No President can order a wiretap. Those restrictions were put in place to protect citizens from people like you."