May 25, 2017 0458 GMT
“President Trump has to provide the American people, not just the intelligence community, but the American people, with evidence that his predecessor, former president of the Unites States was guilty of breaking the law,” McCain told CNN on Sunday.
Earlier this month, Trump accused his predecessor of intercepting his communications at his offices in Trump Tower in New York City just before the November presidential election.
He also said that Obama abused his power and spied on his campaign fearing that his team was connected to Moscow. Trump, however, offered no evidence to support his accusations.
A spokesman of Obama denied that the former president or any White House official had ordered surveillance.
McCain said on Sunday that he had "no reason to believe" Trump's allegations, but if Obama “violated the law” by ordering surveillance, then "we’ve got a serious issue.”
“I have no reason to believe that the charge is true, but I also believe that the president of the Unites States could clear this up in a minute,” McCain said.
The senator added that Trump could call the CIA chief and the director of national intelligence for proof. "All he has to do is pick up the phone, call the director of the CIA, director of national intelligence and say, 'OK, what happened?'"
Experts say electronic surveillance of a US citizen by American intelligence agencies would require a warrant approved by a FISA court judge. Presidents do not have the authority to order such wiretaps and would not even be aware of them as a routine matter.
If the president were involved in the process, it would be "scandalous and unheard of," said Ron Hosko, a former assistant FBI director. Hosko called the allegations "unprecedented” and "unlikely to have occurred in the very broad way” that Trump described.