They call it the "shadow government" or "deep state": the idea that a parallel, hostile group of ex-White House officials and state actors are secretly undermining US President Donald Trump’s government.

In the past, such theories would remain on conspiracy websites, conservative radio talk shows or pop up in tweets from questionable accounts. But with Trump's recent tweets accusing former president Barack Obama of spying on him during the election campaign, the theories have been given new life and to some, credibility.

"Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism!" Trump tweeted from his Mar-a-Lago resort in Florida in the early hours of March 4. He later accused Obama of being a "Bad (or sick) guy".

Obama's spokesman denied the charge but the wiretapping claim has triggered debate and a Congressional investigation.

On Friday, White House Press Secretary Sean Spicer was asked point blank if he believes in the so-called deep state.

"I don’t think it should come as any surprise that there are people that burrowed into government during eight years of the last administration, and may have believed in that agenda and want to continue to seek it," he told reporters.

Clinton allies

Spicer was undoubtedly referring to people such as Mike Morrell, the former acting director of the CIA, Leon Panetta, the former defense secretary, and Eric Holder, the former US attorney general, who all served under Obama.

They made up a group of former high-ranking intelligence, military and White House officials who backed Hillary Clinton as the Democratic presidential nominee last year and would certainly have access to the massive federal bureaucracy that Trump has inherited.

One of the biggest proponents of the deep state theory is conservative radio show host Mark Levin. Less than two days before Trump's tweetstorm of accusations about Obama, Levin argued that rather than looking into the ongoing allegations of Russia's influence over the Trump presidential campaign, the US government needed to pay attention to a "much bigger scandal".

In that show he stated that Obama and supporters of Clinton were "using the instrumentalities of the federal government, intelligence activities, to surveil members of the Trump campaign".

WATCH: The two faces of Donald Trump

In separate interviews, Levin has cited media reports on requests for wiretapping warrants by the FBI, the Office of the Director of National Intelligence (ODNI) and the CIA to look into ties the Trump campaign had with the Russian government.

One New York Times article, in particular, is the centrepiece of Levin's argument.

On January 19, the paper reported on the investigation into a possible Russian connection. "One official said intelligence reports based on some of the wiretapped communications had been provided to the White House," the article stated.

Ned Price worked for the National Security Council for the last three years of the Obama administration. As an official at the NSC, he says the only wiretapping information that would have been provided to them would have been anything related to US foreign policy. He wouldn’t discuss whether any information related to the overall Russian investigation was given to them.

Prior to his NSC job, Price worked at the CIA for eight years. He calls any suggestion of a secret government "delusional" and an insult to "the men and women who have devoted their lives to their country".

When he worked for the CIA, he says, he "never knew if the person sitting next to me was a Republican or a Democrat". Instead, Price argues that the Trump administration is fuelling the deep state idea as a distraction away from the "growing plume of smoke" tying his White House to Russia. "Anything they don't like, they label as fake or conspiratorial or a byproduct of a shadowy deep state," he adds.

'Two miles from the White House'

Still, there are people who believe the deep state is not only real but has a location.

Jack Burkman, Republican strategist and Trump backer, told Al Jazeera recently that the shadow government has set up "two miles from the White House". He would not specify the exact location.

Some groups want the Trump administration to take action.

"All politically motivated deep state shadow operatives must be rooted out of our government, exposed to public disgrace, and banned from ever entering the federal government again," Patrick Howley of the pro-Trump America First Project recently wrote on The Daily Caller.

Jesselyn Radack blew the whistle on human rights violations within the US justice department during the administration of George W Bush.

"There are parts of the intelligence community that works in the shadows," she says. It's the nature of what they do. But any notion they are colluding together against Trump "seems unlikely", she adds. There's simply too much competition within the agencies themselves. "The idea that there is this monolithic deep state is belied by their own infighting."

Radack also questions Trump's wiretapping claim. "It would have operated in secrecy so I'm not sure how Trump would be aware of it," she points out.

Spicer seemed to at least try to answer that question this week when he told reporters, "I think that there has been numerous reports from a variety of outlets over the last couple months that seem to indicate that there has been different types of surveillance that occurred during the 2016 election."

Follow Chris Sheridan on Twitter: @ChrisSheridan34