The Swiss government revealed on Tuesday that it had overestimated pension spending by more than 4 billion Francs ($4.7 billion), which casts doubt on a proposed vote to raise the retirement age for women.

The revelation of this error quickly sparked strong criticism from the left, as the Swiss public, accustomed to referendums, has voted multiple times in recent years on pension reforms based on these financial projections.

In 2033, expenditure on the Swiss pension system “should be around 4 billion Francs lower than had been calculated,” according to the Federal Social Insurance Office, in reference to an “anomaly” linked to “two erroneous formulas.”

This represents a “discrepancy of 6%,” the office added.

Back in 2022, the Swiss public narrowly approved a measure to increase the retirement age for women by one year to 65. The vote highlighted a significant divide, with men largely supporting the reform while women were more opposed.

According to the country’s largest employee organisation with 20 affiliated unions, the Swiss Union of Trade Unions (USS), “it is clear that the extremely close result of the vote on raising the retirement age for women is being called into question.”

“With its alarmist scenarios, the Confederation has decisively influenced pension policy and exerted great pressure to reduce benefits”, the USS stated.

Furthermore, Switzerland’s Green Party also announced on X that they were “examining an appeal” against the vote, which had been “accepted by a narrow majority of 50.5%.”

The Green Party stated: “The financial forecasts for the AHV, on which the Federal Council based its demand to raise the retirement age for women, were wrong.”

In addition, the Swiss Socialist Women party said they were “appalled” and urged for the vote to be “repeated.”

Within the coming days they will be “examining the political and legal options for holding Parliament and the Federal Council to account.”

Other parties also criticised the miscalculation but rejected the left's calls for a re-vote on women’s pensions.

The Federal Department of Home Affairs announced in a statement the opening of an administrative investigation.