A statement declaring that the group of developed and emerging nations will monitor developments for signs of countries artificially deflating their currencies gained a lukewarm welcome from critics who said the G20 had papered over the cracks of a problem that could jeopardise recovery from the financial crisis.
The summit set vague "indicative guidelines" to measure imbalances between their multi-speed economies but – calling a timeout to let tempers cool – left the details to be discussed in the first half of next year.
In the final statement of the summit, the group's fifth since the financial crisis plunged the world into recession in 2008, the leaders vowed to move towards market-determined exchange rates and shun competitive devaluations.
The prime minister, David Cameron, said it was significant the G20 had recognised that global imbalances posed a problem and was alive to concerns of a race to the bottom.
He praised the G20 for putting in place a mechanism that will allow the International Monetary Fund to assess countries and the effects of their exchange rate policies.
Downplaying concerns the issue had been "kicked into the long grass" he said it was significant there was a timetable for addressing concerns at the next G20 summit in France.
He also hailed a point made in the communique that there was a critical, but narrow, window of opportunity to conclude the long-elusive Doha round of trade liberalisation talks launched in 2001.
Washington argued progress towards a more balanced global economy is undermined by China's policy of undervaluing its currency. China has stockpiled its trade surpluses while the US has been left with record trade deficits.
China responded that moves by the Federal Reserve to print money were also having a distorting effect.
"Exchange rates must reflect economic realities … Emerging economies need to allow for currencies that are market driven," US President Barack Obama told a news conference after the communique was agreed.
"This is something that I raised with President Hu [Jintao] of China and we will closely watch the appreciation of China's currency."
Little firm progress
The G20's accord sought to recapture the unity that was forged in crisis two years ago, but deep divides meant the leaders could not venture much beyond what was already agreed by their finance ministers last month.
Negotiators had laboured until the early hours of the morning to thrash out an agreement their leaders could all endorse, despite sharp disagreements that were on public display in the days before the meeting.
In a departure from earlier statements, the G20 said it would allow emerging market countries with "adequate reserves and increasingly overvalued flexible exchange rates" to use "carefully designed macro-prudential measures".
That is a green light for countries such as Brazil, which has already sought to stem massive inflows of capital, to take further measures, short of deliberately engineering a lower exchange rates.
Tempers had flared over the US Federal Reserve's latest $600bn bond-buying programme aimed at strengthening a shaky recovery, while Ireland's worsening debt troubles served as a reminder that the financial system is far from fully healed.
"This hasn't been a love-fest," an official who participated in the negotiations said.
In particular, the leaders were unable to agree on how to identify when global imbalances pose a threat to economic stability, merely committing themselves to a discussion of a range of indicators in first half of 2011.
Tim Condon, head of research at ING Financial Markets in Singapore said it was "hard to disagree" with the vows of the leaders but they had fallen short of the progress hoped for going into the summit.
"They decided just to put down a lot of laudable objectives as the conclusion of the meeting and hope that they can do better, that more can be accomplished in future meetings," he said.
The G20 has fragmented since a global recession gave way to a multi-speed recovery. Slow-growing advanced economies have kept interest rates at record lows to try to kickstart growth, while big emerging markets have come roaring back so fast that many are worried about overheating.
"G20 credibility does depend on showing results … we cannot get out of this with beggar-thy-neighbour policies," Stephen Harper, the Canadian prime minister, said. "We need instead to continue to co-ordinate our actions going forward. The recovery is fragile.
"I don't think the fact that we aren't there yet, we haven't resolved all these problems, means we will fall back."