Outgoing Navi Pillay says 'killers and torturers in Syria have been empowered and emboldened by international paralysis'

The outgoing UN human rights commissioner has launched a blistering attack on the UN security council, saying that "international paralysis" and competing national agendas have cost hundreds of thousands of lives and allowed "killers, destroyers and torturers" in Syria to believe they can act with impunity.

Navi Pillay, whose six-year tenure as UN high commissioner for human rights ends this month, made the comments as figures showed that nearly 200,000 people have been killed in Syria over the past three years.

Analysis by the UN human rights office put the total death toll between March 2011 and the end of April this year at 191,369 – more than double the number of deaths documented a year ago.

"Tragically it is probably an underestimate of the real total number of people killed during the first three years of this murderous conflict," Pillay said on Friday, adding that she deeply regretted that the proliferation of armed conflicts had pushed the humanitarian disaster in Syria "off the international radar".

Speaking a day after the security council unanimously adopted a resolution promising more effort to stop wars, Pillay said it was scandalous that the suffering of the Syrian people was going unheeded.

"The killers, destroyers and torturers in Syria have been empowered and emboldened by the international paralysis," she said. "There are serious allegations that war crimes and crimes against humanity have been committed time and time again with total impunity, yet the security council has failed to refer the case of Syria to the international criminal court, where it clearly belongs."

Her harshest words, however, came on Thursday, when she accused the council – whose permanent members are China, France, Russia, Britain and the US – of a serious dereliction of its duties.

"Short-term geopolitical considerations and national interest, narrowly defined, have repeatedly taken precedence over intolerable human suffering and grave breaches of, and long-term threats to, international peace and security," she said.

Although the council's commitment to human rights had improved significantly during her time in office, said Pillay, "there has not always been a firm and principled decision by members to put an end to crises".

In perhaps her bluntest comments, Pillay said the council's failure to act as one had left thousands dead."I firmly believe that greater responsiveness by this council would have saved hundreds of thousands of lives," she said, adding that countries vetoed moves to stop conflicts were missing the point. "Collective interest – clearly defined by the UN charter – is the national interest of every state."

She called on governments to take proper steps to stop the fighting by cutting off the flow of weapons and military supplies to Syria, and said the council must deploy "rapid, flexible and resource-efficient human rights monitoring missions".

While his tone was far more measured, the UN secretary general, Ban Ki-moon, also called for greater unanimity within the security council. "There is no more important challenge before us than improving our ability to reach a stronger and earlier consensus," Ban told Thursday's meeting. "It is time for a new era of collaboration, cooperation and action from the security council."

Writing further on the subject in the Guardian, Pillay said that while preventing wars was difficult, it was possible.

"There are many examples of countries where the UN – including the office that I have had the honour to serve – has assisted in containing, de-escalating or resolving conflict," she said.

In May this year, the former UN secretary general Kofi Annan also said that diplomatic and political attempts to end the violence in Syria had repeatedly been thwarted by bickering, power play and competing interests. "They have been stymied because of the divisions at the national level, the regional level, and the level of the UN security council," he said. "So we've let the people of Syria down. While we are divided and pointing fingers and accusing each other, they are paying with their lives."

Pillay, who will be succeeded by Prince Zeid Ra'ad Zeid al-Hussein of Jordan, has been an outspoken human rights commissioner.

Last month, she said that Israel may have committed war crimes during its latest offensive in Gaza."There seems to be a strong possibility that international law has been violated, in a manner that could amount to war crimes," Pillay said, citing air strikes and the shelling of homes and hospitals. She went on to condemn Hamas for its "indiscriminate attacks" on Israel.

Pillay has also said the US should not prosecute the whistleblower Edward Snowden, saying his revelations of massive state surveillance were in the public interest.