Updated March 05, 2017 13:04:27

Photo: Donald Trump described Barack Obama as a "bad (or sick) guy". (AP: Pablo Martinez, file)

US President Donald Trump has accused former president Barack Obama of "wire-tapping" his office telephones during last year's election, lodging a startling allegation of abuse of power without evidence or explanation.

In a series of angry morning tweets, Mr Trump suggested his predecessor was behind a politically motivated plot to upend his campaign.

He compared the alleged events to "Nixon/Watergate" and "McCarthyism!", and called Mr Obama a "bad (or sick) guy".

Mr Trump did not offer any evidence or details, or say what prompted him to make the allegations. Mr Obama's spokesman has denied the allegations.

The White House did not respond to questions about what prompted Mr Trump's tweets. Presidents cannot legally order wire-taps against US citizens.

Mr Trump said he had "just found out" the information, though it was unclear whether he was referring to a briefing, a conversation or a media report.

The President has in the past tweeted about unsubstantiated and provocative reports he reads on blogs or conservative websites.

On Thursday, a conservative radio host made claims about alleged steps taken by the Obama administration to influence the election.

That was followed yesterday by far right-wing news outlet Breitbart, which published an article claiming the Obama administration eavesdropped on the Trump campaign.

Mr Obama's spokesman Kevin Lewis said a "cardinal rule" of the Obama administration was that no White House official ever interfered in any Justice Department investigations, which are supposed to be conducted free of political influence.

"As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any US citizen. Any suggestion otherwise is simply false," Mr Lewis said.

Behaviour 'beneath the office of the President'

Mr Trump's claims drew bipartisan rebukes from Democrats and Republicans alike who find his habit of venting on social media to be beneath the office of the President.

He's been in the headlines for meetings with members of US President Donald Trump's team during last year's presidential campaign. But what do we actually know about Russian ambassador to the US, Sergey Kislyak?

Representative Eric Swalwell, a Democrat who is a member of the House Intelligence Committee, downplayed Mr Trump's allegation, saying: "I think this is just the President up early doing his routine tweeting."

"Presidents don't wire-tap anyone. These are pursued by the Department of Justice in accordance with the FBI and signed off by a judge."

Still, the morning tweets stand out given the gravity of the charge and the strikingly personal attack on the former president. Mr Trump as recently as last month spoke fondly of his relationship with Mr Obama, despite their differences.

Members of Congress said Mr Trump's allegations required investigation or explanation.

US Representative Adam Schiff, the top Democrat on the House Intelligence Committee, called Mr Trump's assertion a "spectacularly reckless allegation".

"If there is something bad or sick going on, it is the willingness of the nation's chief executive to make the most outlandish and destructive claims without providing a scintilla of evidence to support them," he said.

Democrat Senator Ron Wyden posted on Twitter: "Either FBI is talking to the subject of an investigation or Trump is making it up. Either way Americans deserve explanation."

Trump defends Sessions meeting

Mr Trump's administration has come under pressure from FBI and congressional investigations into contacts between some members of his campaign team and Russian officials during his campaign.

During his series of tweets, Mr Trump also noted that Russian ambassador Sergei Kislyak had visited the White House "22 times, and 4 times last year alone".

"The first meeting Jeff Sessions had with the Russian Amb was set up by the Obama Administration under education program for 100 Ambs......" he tweeted.

Here are the people who could determine the fate of Trump's Attorney-General.

There have been calls for current Attorney-General Jeff Sessions to resign after it was revealed that he failed to disclose two conversations he had with Mr Kislyak during the presidential campaign.

At his confirmation hearing, Mr Sessions was asked whether "anyone affiliated" with the campaign had contact with Russian officials.

Mr Sessions — formerly a senator and member of the Senate Armed Services Committee — was a fervent supporter of Mr Trump during the campaign.

Mr Trump's national security adviser, Michael Flynn, also resigned in February after revelations that he had discussed US sanctions on Russia with the Russian ambassador to the US before Mr Trump took office.

ABC/wires

Topics: world-politics, donald-trump, us-elections, united-states

First posted March 04, 2017 23:40:41