The price of most popular gasoline at the pumps of PKN Orlen, Poland's top wholesaler and retailer of motor fuel, has stayed unchanged as the company cut wholesale prices of the fuel by a total of 14% on Dec. 31 and Jan. 1, company data shows.

UOKiK has not launched a formal investigation, saying it could not assess the company's practices without a thorough analysis, but "we're not excluding an intervention," its press office said in response to question from Reuters.

MPK Wroclaw, the public transportation operator in Poland's third largest city, believes PKN Orlen's pricing practices "have cost the city" 967,000 zloty ($217,000) in December, CEO Krzysztof Balawejder said in a Facebook post, suggesting the company had kept prices artificially high in December despite falling crude oil prices and an appreciating zloty.

Warsaw will also notify UOKiK about excessive margins of Orlen which have cost the city "millions of losses" mayor of the capital city Rafal Trzaskowski said on Twitter on Tuesday.State-controlled PKN Orlen says it has been keeping pump prices at levels among the lowest in Europe, adding that the cost for buyers depended on the balance of demand and supply, and was partly related to imports.

"In December, the zloty has gained while the price of oil remained stable and this allowed us not to hike prices due to the tax hike, we did it for the benefit of Poles and now we have to explain ourselves," Daniel Obajtek, Chief Executive Officer told reporters on Tuesday. Euro-denominated fuel prices at the pump in Poland remained below the EU average last month amid lowered taxation.

But Poland's price of popular euro-super gasoline net of duties and taxes was the highest in the EU last month, while diesel fuel was the second most expensive in the bloc after Sweden, according to the Weekly Oil Bulletin published by the European Commission.

($1 = 4.4523 zlotys)

(Reporting by Marek Strzelecki; additional reporting by Pawel Florkiewicz; editing by David Evans)