Former Attorney General Michael Mukasey has said it is likely there was surveillance on Trump Tower but the order is unlikely to have come from the White House.

Mr Mukasey, who served under George W Bush between 2007 and 2009, said it is likely that the FBI would have monitored Trump Tower but it would have been authorised by the Attorney General or the Justice Department rather than Barack Obama himself.

He told ABC News: “It means there must have been a basis to believe that somebody in Trump Tower may have been acting as an agent of the Russians for whatever purpose – not necessarily the election – but for some purpose.”

The lawyer said it was common for the FBI to keep track of people who act, or appear to act, as an agent of a foreign government.

“They keep track of people who act as agents of the Chinese, the Russians, the Israelis, everybody”, he explained.

The White House doubled down on the allegations, which Mr Obama has denied, on Sunday when it called for an investigation by Congress but refused to provide any evidence to back up the claim.

Mr Trump tweeted about the allegations on Saturday but they appear to have come from a report by alt-right website Breitbart on Friday which also did not provide any evidence.

It comes as the scandal over his administration’s links to the Kremlin reared its head once more after his Attorney General Jeff Sessions was found to have met with the Russian ambassador during the election campaign.

The controversial orders Donald Trump has already issued Show all 9 1 /9 The controversial orders Donald Trump has already issued The controversial orders Donald Trump has already issued Trump and the media White House Press Secretary Sean Spicer takes questions during the daily press briefing Getty Images The controversial orders Donald Trump has already issued Trump and the Trans-Pacific Partnership Union leaders applaud US President Donald Trump for signing an executive order withdrawing the US from the Trans-Pacific Partnership negotiations during a meeting in the Roosevelt Room of the White House in Washington DC. Mr Trump issued a presidential memorandum in January announcing that the US would withdraw from the trade deal Getty The controversial orders Donald Trump has already issued Trump and the Mexico wall A US Border Patrol vehicle sits waiting for illegal immigrants at a fence opening near the US-Mexico border near McAllen, Texas. The number of incoming immigrants has surged ahead of the upcoming Presidential inauguration of Donald Trump, who has pledged to build a wall along the US-Mexico border. A signature campaign promise, Mr Trump outlined his intention to build a border wall on the US-Mexico border days after taking office Getty Images The controversial orders Donald Trump has already issued Trump and abortion US President Donald Trump signs an executive order as Chief of Staff Reince Priebus looks on in the Oval Office of the White House. Mr Trump reinstated a ban on American financial aide being granted to non-governmental organizations that provide abortion counseling, provide abortion referrals, or advocate for abortion access outside of the United States Getty Images The controversial orders Donald Trump has already issued Trump and the Dakota Access pipeline Opponents of the Keystone XL and Dakota Access pipelines hold a rally as they protest US President Donald Trump's executive orders advancing their construction, at Columbus Circle in New York. US President Donald Trump signed executive orders reviving the construction of two controversial oil pipelines, but said the projects would be subject to renegotiation Getty Images The controversial orders Donald Trump has already issued Trump and 'Obamacare' Nancy Pelosi who is the minority leader of the House of Representatives speaks beside House Democrats at an event to protect the Affordable Care Act in Los Angeles, California. US President Donald Trump's effort to make good on his campaign promise to repeal and replace the healthcare law failed when Republicans failed to get enough votes. Mr Trump has promised to revisit the matter Getty Images The controversial orders Donald Trump has already issued Donald Trump and 'sanctuary cities' US President Donald Trump signed an executive order in January threatening to pull funding for so-called "sanctuary cities" if they do not comply with federal immigration law AP The controversial orders Donald Trump has already issued Trump and the travel ban US President Donald Trump has attempted twice to restrict travel into the United States from several predominantly Muslim countries. The first attempt, in February, was met with swift opposition from protesters who flocked to airports around the country. That travel ban was later blocked by the Ninth Circuit Court of Appeals. The second ban was blocked by a federal judge a day before it was scheduled to be implemented in mid-March SANDY HUFFAKER/AFP/Getty Images The controversial orders Donald Trump has already issued Trump and climate change US President Donald Trump sought to dismantle several of his predecessor's actions on climate change in March. His order instructed the Environmental Protection Agency to reevaluate the Clean Power Plan, which would cap power plant emissions Shannon Stapleton/Reuters

Mr Sessions, who has since recused himself from the investigation into apparent Russian interference in last year's presidential election election by Justice Department, told Congress – under oath – he had no dealings with Russia during the campaign.

The former Alabama senator was a key advisor on foreign policy during Mr Trump’s campaign and served as vice-chairman of his transition team.

The question of Russian meddling has haunted the Trump administration since his surprise victory in November.

Russian hackers were widely blamed for the leak of a series of damaging emails exchange between leading members of the Democratic National Committee (DNC).

In the days following the leak, Mr Trump gleefully called for Russian agents to hack in his rival Hillary Clinton’s emails from the time she was Secretary of State.