Trump revives unproven conspiracy theory that Obama administration 'spied' on his campaign

President congratulates Michael Flynn after judge ruled Justice Department must drop its case against him

Reviving his so-far unproven "Obamagate" conspiracy theory, Donald Trump on Wednesday again contended the Obama administration "spied" on his 2016 campaign.

"The Obama administration spied on a campaign," the president said several times during brief remarks alongside his Polish counterpart in the Oval Office.

Mr Trump made the remarks as part of a congratulatory message he sent to Michael Flynn, the retired Army three-star general and his first White House national security adviser.

A federal judge ordered the Justice Department earlier in the day to drop its case against Mr Flynn. He had been charged with twice lying to federal investigators about his communications with then-Russian Ambassador Sergey Kislyak during the presidential transition after Mr Trump's 2016 win. Trump critics, including many congressional Democrats, have accused the president and Attorney General William Barr of intervening in the probe and orchestrating a decision to drop the charges.

But Mr Trump, during his first of the day's two planned media appearances, was focused on his predecessor, as he so often is.

"There's never been anything like that around," Mr Trump said of his conspiracy theory about the Obama administration. He claimed that if a Republican administration had done what he claims Barack Obama's did, those GOP officials would be in jail "for 50 years."

The "Obamagate" theory maintains that the 44th president and his top intelligence chiefs sought to entrap incoming Trump officials in legal controversies to kneecap Mr Trump's presidency from the start.

Some aspects of the president's theory have yet to be corroborated, but he and his top aides and surrogates are pushing the narratives by asking questions about the motives of a number of individuals who were senior members of the Obama administration's national security, intelligence and foreign policy team.

The president did not respond to questions about whether he has spoken to Mr Flynn about Wednesday's court ruling.