The new leader of Amnesty International has said the Trump administration’s separation of families at US borders is “one of the worst atrocities” the world has seen in a long time.

Kumi Naidoo said many world leaders – especially US president Donald Trump – are reversing hard-won human rights gains.

The South African-born former anti-apartheid activist began a four-year term at the helm of the human rights group on Wednesday.

He said the challenges to human rights in the world today mean that his organisation must show “maximum courage”.

Mr Naidoo singled out the governments of Saudi Arabia, Hungary, Yemen and the Philippines as ones he says are failing to respect human rights.

The new Amnesty chief said: “The presidency of Donald Trump is a major challenge for the people of the US and the people of the world.”

Saying the psychological damage of the border separation policy alone could be long-lasting, he added: “Overall on human rights he has set us back … and it should be no surprise that Donald Trump will be in my vision of activism and will be somebody who will receive quite close focus by Amnesty as a global movement.”

With a background of activism against apartheid in his native South Africa and for environmental issues as a director of Greenpeace, Mr Naidoo said he intends to make Amnesty “bigger, bolder and more inclusive”.

He added: “What I hope to do at Amnesty is to intensify our appetite for peaceful civil disobedience.”

Kumi NaidooMr Naidoo has said he wants to encourage civil disobedience (AP)

Although world leaders often ignore letters and meetings, he said that “when you mobilise thousands of people on their doorstep … that seems to work much better”.

Mr Naidoo added: “We should not allow the shrinking democratic space to prevent us from having a more robust and more courageous activism that will include peacefully resisting unjust laws and breaking unjust laws where necessary.”

Despite the recent setbacks for human rights, Mr Naidoo said he is optimistic. Amnesty currently has a global membership of seven million people and he said he would like to see that increase to 70 million, especially among younger people.

He said: “Young people will not accept wisdom that they are the leaders of tomorrow, they will assert their leadership now.”