Britain will try to reform the G8 when it chairs the group in 2013, narrowing its focus to foreign policy and security, and could even combine meetings with Nato summits, premier David Cameron said.

The broader G20, comprising developed and developing countries, would remain the main economic forum for world leaders, a status it achieved during the global financial crisis, he said.

"When it comes to the UK's turn in 2013 there is an opportunity to change the way the G8 works," Mr Cameron told reporters on his flight home on Monday from summits of the Group of Eight rich nations and the Group of 20 in Canada.

"You could make it more focused and strategic, majoring on foreign policy and security issues, while also keeping the particular link to accountability on development aid which is really important.

"But you could consider getting rid of the pre-cooked communique, to turn it into a proper small strategic discussion."

The Prime Minister said the G8 could be allied to foreign affairs events such as meetings of Nato and the United Nations, which would leave the larger G20 to discuss economic issues.

"You could look at attaching the G8 to another international event. It might be a Nato summit or UN meeting. That would also help reduce costs," he said, according to comments received by AFP on Tuesday.

"That would leave the G20 to be the big economic global governance forum, which it now is. The G20 has after all earnt its spurs from its vital work on financial regulation and economic co-ordination."

But Mr Cameron said the G8 would not "die out" - rich democracies meeting "for a strategic discussion, to hammer out a common view on things like Afghanistan, Iran and Middle East peace process, is still a really important thing to do".