David Cameron has joked that he does not have to listen to US president Donald Trump's "wiretapped" conversations anymore, now that he is no longer prime minister.

In a speech at Brown University, the American Ivy League institution on Monday evening, Mr Cameron addressed the unsubstantiated White House suggestions that GCHQ had helped Barack Obama spy on Mr Trump.

"Just to be clear, that's a joke," he added, to laughter from the 2,000 students at the Rhode Island university.

According to the Providence Journal, Mr Cameron also said in the wide-ranging address that: