The European Commission  is concerned that reintroducing a different retirement age for men and women in Poland could violate the bloc’s equality rules, according to a letter from Brussels.

Poland’s ruling Law and Justice (PiS) party and President Andrzej Duda – who comes from the same political grouping – campaigned on promises to undo a 2012 reform that had been gradually raising and equalising the retirement age at 67.

The government’s change, largely popular among Poles, will take effect from October, reintroducing a retirement age of 65 for men and 60 for women.

“Equal treatment between women and men is a key pillar on which our Union is based,” top EU officials for justice and gender equality, Vera Jourova, and employment and social affairs, Marianne Thyssen, wrote.

“The Commission has concerns about the changes in the Polish statutory pension system which might be incompatible with EU law.”

Poland’s Deputy Prime Minister Mateusz Morawiecki defended the government’s change, saying women should have the right to retire earlier because they have more responsibilities, including raising children.

“The role of women must be appreciated and therefore the legislators provided for the possibility of an earlier retirement,” Morawiecki told the Catholic Trwam television when asked to comment on the Commission’s letter.

“What we propose reflects not only social expectations but also different roles for women, different roles for men.”

Economists have warned the Polish move will hit growth and public finances, at a time when the PiS has already sharply increased state spending.

Brussels has already raised the issue in its criticism of separate PiS-sponsored legal moves to put courts and judges under more direct government control.