Amnesty International has urged the five permanent members of the UN Security Council to give up their power of veto in cases where atrocities are being committed.
In its annual report, the rights group said the global response to an array of catastrophes in 2014 had been shameful.
Richer countries were guilty of taking an “abhorrent” stance by not sheltering more refugees, Amnesty said.
The outlook for 2015 was bleak, the group added.
Saying that 2014 had been a catastrophic year for victims of conflict and violence, Amnesty said world leaders needed to act immediately to confront the changing nature of armed conflict.
In its 415-page report detailing abuses in 160 countries, the group accused governments of “pretending the protection of civilians is beyond their power”.
It said millions of civilians had been killed from Syria to Ukraine, Gaza to Nigeria, while the number of displaced people around the world exceeded 50 million last year for the first time since the end of World War II.
“As people suffered an escalation in barbarous attacks and repression, the international community has been found wanting,” Amnesty said.
Salil Shetty, the organisation’s secretary-general, said in a statement that the United Nations Security Council had “miserably failed” to protect civilians.
Instead, the council’s five permanent members – the UK, China, France, Russia and the US – had used their veto to “promote their political self-interest or geopolitical interest above the interest of protecting civilians,” Shetty said.
Part of the solution would be those countries surrendering their Security Council veto on issues related to mass killing and genocide, Amnesty added.
This proposal is similar to a push being led by France with the backing of 70 countries, but Amnesty hopes its support will give the idea fresh impetus.
It believes the move would give the UN a better chance to save civilian lives in conflict zones.
Last year, the veto was only used twice in the UN Security Council.
In March, Russia vetoed a resolution condemning as illegal a referendum on the status of Crimea and in May Russia and China blocked a resolution condemning Syria.
But many draft resolutions proposing tough action to deal with crises never reach the voting stage because they would almost certainly be vetoed.
The Amnesty report argues that if the use of the veto in the Security Council had already been restrained in the way the report suggests, that could have made it impossible to block UN action over the violence in Syria.
This might have resulted in Syrian President Bashar Al-Assad being referred to the International Criminal Court, greater access for badly needed humanitarian aid would have been possible and civilians helped more.