A report murdered MP Jo Cox was working on before her death that warns Britain must not shy away from military action has been published.

In the weeks before she was killed in a brutal attack by a neo-Nazi, the Labour backbencher had started to put together a joint paper with Conservative Tom Tugendhat about the UK's role in the world.

Widower Brendan Cox said his wife had written on a draft of the report, which was completed by her friend MP Alison McGovern, that "Britain must lead again".

The backlash over the Iraq war has led to a rise in "knee-jerk isolationism, unthinking pacifism and anti-interventionism", according to The Cost of Doing Nothing paper.

But retreating from the global stage has "dangerous" implications for national and international security and heightens the risk of further global instability, it warns.

Mr Cox said: "Jo was passionate about this piece of work. She felt deeply that the UK had a duty to stand up for civilians threatened by war and genocide.

"Her commitment wasn't theoretical, it was forged by her experience of meeting survivors of genocide in Kosovo, Bosnia, Rwanda and Sudan.

"Last week I was clearing some of Jo's things and found the first draft of the report that she had scribbled all over. At the top she had written 'Britain must lead again'.

"Although she isn't here to advance that argument, she'd be delighted that her colleagues and friends are able to do so in her stead."

The report, published by Policy Exchange, highlights examples of successful intervention, including the introduction of a no-fly zone in northern Iraq in 1991 to protect Kurds from air attacks waged by Saddam Hussein's regime and Nato's action a year earlier to shield civilians in Kosovo from Slobodan Milosevic's campaign of ethnic cleansing.

It also sets out the "devastating consequences" of failing to take action, including in the 1994 Rwandan genocide and Syrian civil war, which has left an estimated half a million people dead.

Mr Tugendhat said: "Britain has never been isolationist. It is in our national interest to be engaged with the world we helped shape.

"That means taking responsibility, and influencing events and intervening when necessary. To stand aside would not make us or the world safer, but leave us vulnerable to the whims of others rather than doing what we have always done - shape our own destiny and be a force for good."

Ms McGovern, MP for Wirral South, said: "We cannot simply look the other way in cases of war crimes, crimes against humanity or genocide.

"Jo never believed that simply doing nothing in the face of atrocities was good enough, and neither should we."

Former Prime Minister Gordon Brown, who will launch the report, said: "In her last speech in the House of Commons, Jo Cox said that 'sometimes all it takes for evil to triumph is for good men to do nothing'.