British Foreign Secretary William Hague, speaking after talks with his counterparts, admitted the world had done too little to try to resolve Syria's two-year-old conflict, in which an estimated 70,000 people have been killed.
"The United Nations Security Council has not fulfilled its responsibilities because it is divided. That division continues. Have we solved that division at this meeting? No. We didn't expect to do so," Hague told reporters.
"The world has failed so far in its responsibilities and continues to do so."
North Korea's threats of war and Iran's nuclear programme were also high on the agenda of the ministers' talks in London but little substance came out of their private meetings with members of Syria's opposition on the sidelines of the gathering.
Actress Angelina Jolie, a goodwill ambassador for the United Nations High Commissioner for Refugees, addressed the ministers, urging more action to prevent sexual violence against women in conflict zones.
On North Korea, the G8 condemned Pyongyang's development of nuclear weapons "in the strongest possible terms" but announced no specific steps.
In a communiqué issued after the meeting, foreign ministers from the United States, Britain, France, Germany, Italy, Japan, Canada and Russia urged North Korea to "refrain from further provocative acts".
"If the DPRK (North Korea) conducts another missile launch, or nuclear test, we have committed ourselves to take further significant measures," Hague said, without giving more details.
A U.S. official, speaking to reporters on condition of anonymity, said the ministers had discussed the role of China - which is not part of the G8 - in addressing North Korea's threats, but that nothing specific had come out of the talks.
"SPRINGBOARD" FOR JIHADISTS
With diplomatic efforts deadlocked, Syria's protracted conflict remains the biggest headache for global powers, and Hague described it as the world's top destination for jihadists.
The rebel al-Nusra Front fighting President Bashar al-Assad pledged allegiance to al Qaeda leader Ayman al-Zawahri on Wednesday, fuelling concerns that Syria could become a hotbed for Islamist militants in the region.
"Moscow is seriously concerned with a bigger interest in Syria on the part of al Qaeda, the observed plans by international terrorists to turn this country into their main springboard in the Middle East," Russia's Foreign Ministry said in a separate statement on Thursday.
Leaders of the Syrian National Coalition were present on the sidelines of the London meeting to ask for more humanitarian help but no promises were made, according to officials.
In their statement, the ministers "called for greater humanitarian assistance and for improved and safe access to the Syrian people by humanitarian agencies in co-ordination with all parties to the conflict".
On Iran, they expressed concern about the lack of progress in the latest talks aimed at resolving a decade-long nuclear dispute that threatens to trigger a new war in the Middle East.
"People were concerned about that, that time is not unlimited," the U.S. official said.
"They didn't feel that the Iranians were bringing anything significant to the table, or anything new."
