Brendan Cox said late on Saturday he had acted inappropriately and would leave his positions at the Jo Cox Foundation and the More in Common charity. Both were started after a far-right extremist fatally shot and stabbed MP Jo Cox just before the 2016 Brexit referendum.

Brendan Cox said he wanted to apologise "deeply and unreservedly" for his past behaviour while working at another charity.

"I do acknowledge and understand that during my time at Save the Children I made mistakes and behaved in a way that caused some women hurt and offence," Cox said in a statement. He promised to hold himself to "much higher standards" in the future.

The allegations against Cox surfaced last week in Britain's Mail on Sunday. He called the newspaper's reports a "massive exaggeration" but admitted making mistakes.

On Sunday, the paper published what it said was a tearful interview with him in which he expressed remorse about his behaviour.

Charities in the UK have been under increased scrutiny in recent weeks following allegations reported by the Times of London that senior staff from British aid organisation Oxfam used prostitutes and downloaded pornography while working in Haiti after the 2010 earthquake.

Jo Cox's family offered support for Brendan Cox, praising him on Sunday for taking responsibility for prior misdeeds. Her sister, Kim Leadbeater, said Cox "did the right thing" by admitting inappropriate behaviour.

"As a family we will support Brendan as he endeavours to do the right thing by admitting mistakes he may have made in the past, and we respect him for doing so," she said. "We all make mistakes. Brendan is a wonderful father, and I have no doubt about the happiness he brought to Jo."

Cox has campaigned publicly for causes his wife supported since her death.

She was a Labour Party MP opposed to Brexit who was killed by a far-right extremist now serving a life sentence for murder.

Australian Associated Press