WARSAW, Sept 7 (Reuters) - Poland's central bank governor refused to be drawn on when and how much rates will fall further, speaking a day after a bigger-than-expected rate cut shocked investors and sent the zloty currency tumbling.

Wednesday's decision to cut the cost of credit to 6.00% from 6.75% blindsided economists who had expected 25 basis points of easing or no change at all. The move provoked accusations that it was designed to help the government ahead of October elections and would hamper the fight against inflation.

"We are not announcing anything, we are observing the situation," Adam Glapinski told a news conference on Thursday. "If inflation will quickly go towards 5% and then below 5%, interest rates will decrease ... but it is difficult to say how much they will decrease."

Glapinski said he would be serving champagne when inflation reached 5%. The central bank targets inflation of 2.5% plus or minus one percentage point.

The zloty fell sharply while he was speaking and was trading around 1% down on the day against the euro at 4.6185 at 1446 GMT, following a 1.8% drop on Wednesday.

Glapinski said the bank had no target for the currency or plans to intervene to defend the zloty, describing its current level as "OK".

He also rejected accusations that politics had played a role in Wednesday's decision.

"There is no political context to the decision here," he said. "We made it only when we were sure that the economy is definitely on a course of rapidly falling inflation."

Donald Tusk, the leader of Poland's largest opposition party, said earlier on Thursday that Glapinski was "fully involved in politics and elections."

Glapinski said the central bank moved after its day-to-day tracking showed inflation had fallen to single digits, a condition he had previously set for cutting rates.

A statistics office flash estimate showed year-on-year inflation at 10.1% in August.

Glapinski said it will fall to just over 8.5% in September before reaching 6-7% at the end of the year.

(Reporting by Anna Koper; Pawel Florkiewicz; Alan Charlish; Karol Badohal; writing by Anna Wlodarczak-Semczuk and Alan Charlish; editing by Justyna Pawlak and Tomasz Janowski)