* Sterling falls 8 pct to low since Plaza Accord

* Safe-haven yen rallies, dollar drops below 100.00 yen

* Dollar index up 3 pct, biggest daily gain since 1978

By Ian Chua and Hideyuki Sano

SYDNEY/TOKYO, June 24 (Reuters) - Sterling suffered its most volatile session in living memory and hit its lowest level since the 1985 Plaza Accord as the Leave camp looks increasingly likely to win Britain's referendum on its EU membership, triggering a rush into the safe-haven yen.

The euro also dropped more than three percent against the dollar while the Swiss franc firmed along with the yen, though the wild moves made traders wary of intervention by Group of Seven countries.

The pound fell as much as 9.4 percent to $1.3462 , its cheapest level since September 1985, when five major economies at the time agreed to weaken the dollar. At 0345 GMT, it was hovering at $1.3509.

"It is wild," said Shane Oliver, Head of Investment Strategy and Chief Economist at AMP Capital in Sydney.

"There is still a way to go yet," Oliver added. "Even if the vote is to leave, there is a lot of water to go under the bridge before Britain actually leaves the EU. We don't know what sort of deal they are going to cut with the EU."

Against the yen, sterling ricocheted between 135.30 and 160.14 and was last at 137.32, down a massive 13 percent on the day.

The euro rose 6 percent to 81.20 pence , hitting its highest level in more than two years.

The euro fell 3.6 percent against the dollar to $1.0975 , a low last seen in March.

The plunge in European currencies lifted the dollar index 3 percent, which, if sustained, would be its biggest daily gain since 1978.

The sharp moves raised worries that global policymakers may take action to support the pound.

"We need to be careful about intervention in such a case. I think there's more than enough excuse for G7 to intervene," said Koichi Yoshikawa, executive director of finance at Standard Chartered Bank.

As Brexit anxiety grew, so too has demand for the safe-haven yen, which jumped on the greenback and euro.

The greenback dropped to 99.00 yen, a fall of 6.7 percent, before gaining a semblance of stability at 101.50 yen, the first time it fell below the 100 mark since late 2013.

The euro fell to as low as 109.50 yen for the first time since late 2012.

The safe-haven Swiss franc also gained against the euro, which fell to 1.0710 franc , its lowest since August.

(Additional reporting by Hideyuki Sano in Tokyo and Rebecca Howard in Wellington, Editing by Eric Meijer and Sam Holmes) ((ian.chua@thomsonreuters.com; +61 2 9321 8174; RM: ian.chua.thomsonreuters.com@reuters.net))