Britain’s new prime minister, Andy Burnham, has said he is prepared to criticise and publicly oppose US President Donald Trump whenever doing so serves Britain’s national interests.

In his first extensive interview since taking office, Burnham said he had held a productive conversation with Trump and described the US president as “very warm.”

However, when asked twice whether he trusted Trump, Burnham avoided giving a direct answer.

“The world is changing, isn’t it?” he said, adding that leaders must respond to events as they develop.

Burnham said he could not promise that he would always agree with Trump or rule out expressing a different position whenever Britain’s interests required it.

“I could never say that I will not take a different view from Trump, or that I will not need to express a different position if that is right for Britain,” he said.

The prime minister also emphasised that his political strength came from maintaining close contact with ordinary people, something he said would not change after entering Downing Street.

Asked whether he would openly criticise and challenge Trump if circumstances demanded it, Burnham replied that defending the national interest must come before everything else.

“That is what doing this job properly requires,” he said.

Burnham also expressed concern over Trump’s decision to initiate the conflict with Iran, adding that he would not hesitate to speak publicly when he believed doing so was right.