WARSAW, Aug 11 (Reuters) - Poland's foreign currency loans conversion bill, if implemented in its current form, could cost the country's banks about 22 billion zlotys ($5.75 billion), a document from the financial regulator KNF published by state news agency PAP showed.

In the document KNF estimated that about a third of all mortgages denominated in Swiss francs and euros would fulfill the conditions of the new bill and be eligible for conversion into zlotys.

KNF also said that for ten surveyed banks the estimated cost of conversions exceeds their 2014 net profit, while for six of them the cost was more than three times their last year profit.

Last week, Polish parliament's lower chamber passed a law allowing some foreign currency mortgage holders to convert their loans into zlotys. The bill still needs to be approved by the senate and signed by the president to enter into law.

($1 = 3.8254 zlotys) (Reporting by Agnieszka Barteczko; Writing by Marcin Goettig)