Alongside plans billed as helping speed infrastructure funding in developing countries and a shift to renewable and sustainable technology, the world's seven largest advanced economies again pledged to meet the climate finance target.

But climate groups said the promise made in the summit's final communique lacked detail and the developed nations should be more ambitious in their financial commitments.

In the communique, the seven nations - the United States, Britain, Canada, France, Germany, Italy and Japan - reaffirmed their commitment to "jointly mobilise $US100 billion ($A130 billion) per year from public and private sources, through to 2025".

"Towards this end, we commit to each increase and improve our overall international public climate finance contributions for this period and call on other developed countries to join and enhance their contributions to this effort."

After the summit concluded, Canada said it would double its climate finance pledge to $C5.3 billion ($A5.7 billion) over the next five years and Germany would increase its by 2 billion to 6 billion euros ($A9.4 billion) a year by 2025 at the latest.

British Prime Minister Boris Johnson, host of the gathering in Carbis Bay, told a news conference that developed nations had to move further, faster.

"G7 countries account for 20 per cent of global carbon emissions, and we were clear this weekend that action has to start with us," he said as the summit concluded on Sunday.

"And while it's fantastic that every one of the G7 countries has pledged to wipe out our contributions to climate change, we need to make sure we're achieving that as fast as we can and helping developing countries at the same time."

Some green groups were unimpressed with the climate pledges.

Climate Action Network director Catherine Pettengell said the G7 had failed to rise to the challenge of agreeing on concrete commitments on climate finance.

"We had hoped that the leaders of the world's richest nations would come away from this week having put their money where their mouth is," she said.

European Commission President Ursula von der Leyen said the G7 leaders had agreed to phase out coal but the communique seemed less clear.

"We have committed to rapidly scale-up technologies and policies that further accelerate the transition away from unabated coal capacity, consistent with our 2030 NDCs and net zero commitment," it said.

The leaders also pledged to work together to tackle so-called carbon leakage - the risk that tough climate policies could cause companies to relocate to regions where they can continue to pollute cheaply.

But there were few details on how they would manage to cut emissions, with an absence of specific measures on everything from the phasing out of coal to moving to electric vehicles.

Australian Associated Press