By David Lawder

WASHINGTON (Reuters) - Foreign exchange markets are not "disorderly" in the wake of Britain's vote to leave the European Union and there is no need for the Group of 20 major economies to broadly agree to tame them, the International Monetary Fund's chief economist said on Tuesday.

A number of currencies have fallen sharply against the dollar since the June 23 EU referendum in Britain, including the pound, the euro and China's yuan, while the yen has also seen more volatility as well.

Maury Obstfeld, the IMF's chief economist, said flexible exchange rates have acted as a buffer to shocks such as the Brexit vote, and most often provide important price signals that guide economic activity, allowing countries to pursue monetary and fiscal policies suited to their economic needs.

"So I sort of reject the premise that volatility needs to be tamed," Obstfeld said in a news conference, adding that a G20 repeat of the 1985 Plaza Accord deal to stabilize currency rates was "simply not something that's going to happen."

He also said another Bank of Japan intervention to stem excessive yen strength - Japanese officials have described forex markets as "nervous" since the Brexit vote - would not be "necessary or useful" in boosting Japan's moribund economy..

While there may be a case for intervention when markets become," Obstfeld said he has not seen such movements, including in Japan.

"We have seen some currency volatility in recent weeks, but we would not characterize conditions in the yen market as being disorderly conditions," he said, adding that Japan was better off pursuing policies to increase wages, add fiscal stimulus and implement structural economic reforms.

"We don't view intervention as being a necessary or useful part of that package," Obstfeld said.

The IMF earlier on Tuesday cut its global growth forecasts for 2016 and 2017 because of the uncertainty over trade, investment and market confidence created by the Brexit vote.

Brexit and its aftermath will be a key topic on the agenda when the G20 finance ministers and central bank governors meet this weekend in Chengdu, China, amid calls for measures to boost growth and ensure financial market stability.

IMF Managing Director Christine Lagarde will be among the participants in the meeting.

(Reporting by David Lawder; Editing by Paul Simao)