WARSAW, July 24 (Reuters) - Poland's president said he would refer a bill introducing a windfall tax on oil and gas companies' profits to the country's constitutional court, pointing to concerns about its retroactive nature and potential effect on consumers.

The Polish parliament has approved the bill to tax windfall profits generated by oil and gas companies which have benefited from surging margins amid supply shocks due to the Middle East war.

The bill assumes that 2026 revenues on sales of fuels exceeding the previous year average by 20% would be taxed at 60%, generating 4 billion zlotys ($1.05 billion) for the state budget, but it needs final approval from President Karol Nawrocki.

The president said he had doubts about the bill as it would apply retroactively, to revenue generated as far back as March.

"In a democratic state governed by the rule of law, citizens and entrepreneurs must know which regulations are in force at the time they make their decisions," he said in a recorded statement posted on X.

He also said he was concerned that the tax would be passed onto consumers in higher prices, making life difficult for people already struggling with surging energy costs.

"I cannot accept a situation where an attempt to patch up state finances is presented to citizens as a measure to protect their interests, when the actual result will be another wave of price hikes," he said.

The Polish president must sign bills for them to become law. He can also veto them or refer them to the Constitutional Tribunal, the constitutional court.

($1 = 3.7969 zlotys)

(Reporting by Alan Charlish and Anna Koper; Editing by Susan Fenton)

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