KNF estimates the likely cost of the presidential bill on conversion of Swiss franc-denominated mortgages at PLN67bn (€15.6bn), the Polish financial market regulator said in a report on March 15.

The figure is based on the "most likely scenario" for the scheme. KNF warns that such as cost would threaten the stability of some lenders, and lead to a “loss of trust in the banking system". However, officials have already suggested that the draft bill will be redrawn.

“In an extreme case, [the conversion] could cause a financial crisis,” KNF warned. The watchdog was charged with providing an estimate in January, as the president's office unveiled a set of undetailed proposals included in the draft.

The report is likely to push Polish President Andrzej Duda to officially drop the current proposal, according to which borrowers would be allowed to make further payments on their loan at a “just exchange rate,” reached by a comparison of the cost of the forex loan compared with a zloty-denominated loan.

Before KNF’s released its estimate, a number of other estimates suggested the cost of conversion at tens of billions of zloty. That has seen numerous officals, including the presidential office, suggest changes are possible. The chancellery of the president said on March 15 that it is reviewing the KNF assessment.

“The chancellery considers KNF’s calculations as basis for further discussion about the final shape of the [conversion scheme]. For the chancellery, the priority is helping the borrowers while retaining the state’s and the banking sector’s financial stability,” it said in a statement.