* Finance Minister Jan Pociatek offers resignation
* Prime Minister Robert Fico says will consider offer
* Fico says Pociatek behaved unethically
(Adds PM Fico's comment, analyst)
By Martin Santa
BRATISLAVA, June 20 (Reuters) - Slovak Finance Minister Jan Pociatek said on Friday he will offer his resignation following a sharp appreciation of the crown currency hours before it was formally revalued last month.
Prime Minister Robert Fico said Pociatek had behaved unethically by having a social meeting with an investor the weekend before the devaluation, and he would take this into account in considering his response to the offer.
Slovakia revalued the crown's central rate within the European Union's ERM-2 exchange rate mechanism by 15 percent on May 28. The crown jumped 1.4 percent before the official news of the revaluation was issued in the late evening.
The opposition has said there may have been a leak of information to investors by the government, an accusation Pociatek has repeatedly denied.
However, he has said he made a mistake by having a social encounter with an investor from a private equity group on a yacht in Monaco the weekend before the revalation.
"Despite the fact that the finance minister did not do anything illegal, he does not want this case to harm the (ruling) Smer-SD party," Pociatek said in a statement issued by the Finance Ministry.
He said he would tender his resignation to Fico once he returns from an EU summit in Brussels.
UNETHICAL
Speaking in the Belgian capital before beginning his journey back to Bratislava on Friday, Fico said: "I will never accept the resignation because of the leak allegations made by the opposition."
"The only reason I will take into consideration was this unethical behaviour," he added, refering to the Monaco meeting.
Pociatek said on Wednesday the revaluation was a response to the market move earlier in the day, not its cause, and Fico confirmed this.
The central bank (NBS) has however started investigating what it says was unusually high trading volume of about 800 million euros ($1.2 billion) before the revaluation. The market's daily average is around 300 million euros.
Former finance minister Ivan Miklos, now in opposition, said two private equity groups were buying large volumes of crowns ahead of the revaluation and local media reported Pociatek met one of the groups in Monaco the weekend before the decision.
It was an investor from one of these groups whom Pociatek met in Monaco.
Pociatek's offer to resign came on the day that EU leaders gave the final green light for Slovakia to adopt the euro on Jan. 1, 2009.
"Normally, a day after such a decision I would carry the minister on my shoulders," Fico said.
The leftist Fico, who won 2006 general election on a pledge to better care for the poor and cut government ties to big business, has proved he does not hesitate to reshuffle his cabinet, having already presided over several departures.
(Writing by Jan Lopatka; Editing by Gerrard Raven)