Next month voters will be asked if pensions should pay a 13th monthly payment.
Backers say pensioners are struggling with the cost-of-living crisis. But those against point out it will be too much of a strain on the pension fund.
In an extremely rare move, five former federal councillors have written an open letter urging voters to reject the extra payment.
The letter has been signed by Adolf Ogi, Doris Leuthard, Pascal Couchepin and Johann Schneider-Ammann.
Former government ministers normally stay quiet on politics after they leave office.
Unions backing the extra payments have criticised the intervention. They point out the former ministers receive a very generous pension of CHF 23,000 a month and can’t take away CHF 2,000 a month from poorer pensioners.
The vote will be on March 3rd, but ballot papers are now being delivered and many will vote early.