Prime Minister Malcolm Turnbull says he is confident of a "strong" free trade agreement with Britain after meeting with British Prime Minister Theresa May at the G20 today.

Key points: World leaders under pressure to work out a joint approach to revive global growth

World leaders under pressure to work out a joint approach to revive global growth Malcolm Turnbull says he is keen for Australia to clinch Britain's first post-EU trade deal

Malcolm Turnbull says he is keen for Australia to clinch Britain's first post-EU trade deal He will take part in talks on targeting international tax avoidance

Mr Turnbull's meeting with the British Prime Minister, in which he laid the groundwork for a post-Brexit deal, was held on the sidelines of the summit in China, where world leaders are under pressure to work out a joint approach to revive global growth on the final day of the G20 summit.

Leaders of more than 20 nations at the summit are yet to forge a clear plan to recharge the global economy.

Addressing media after meeting with Mrs May, Mr Turnbull said Britain faced enormous challenges in the post-Brexit environment.

He said Australia was providing assistance to Britain in order to negotiate a "very strong, very open" agreement.

"They don't have any trade negotiators," he said.

"They haven't had to negotiate a trade agreement for over 40 years because they've been part of the European system.

"So Theresa May is very grateful as she said for the assistance we've provided."

Mr Turnbull also warned against protectionism, though he acknowledged the public may need more information.

"We need to do a better job of explaining the benefits of trade, of open markets," he said.

He will also meet French President Francois Hollande at the G20, and take part in talks on targeting international tax avoidance — a key focus for the summit.

Leaders are striving to come up with a joint statement on fresh ways to revive the global economy before the summit ends.

But a common theme is a push back against rising calls for protectionist policies.

Talks with Xi against background of investment concerns

Sorry, this video has expired China's Xi Jinping hosts world leaders at G20 Summit ( Political editor Chris Uhlmann )

Mr Turnbull met Chinese President Xi Jinping on the sidelines of the meeting over the weekend, against the background of increasing concerns in Australia over Chinese investment.

China's state media said President Xi urged Australia to create a "fair, transparent and predictable environment" for foreign investment, in the wake of recent decisions by Australia to block Chinese bidders from major electricity and agricultural sales.

"We mostly say yes, we invariably say yes, but from time to time we say no, and we make no bones about that, and China respects it," Mr Turnbull said.

He also emphasised that it was easier for Chinese companies to invest in Australia than for Australian companies to invest in China.