Women with Swiss jobs earn 19.3 percent less than their male counterparts, according to a report issued on Thursday by Eurostat, the European statistical agency.
That is greater than the 16.4 percent average gender pay gap for countries in the European Union based on data from 2013.
And the report, issued ahead of International Women’s Day on Sunday, shows the gap in Switzerland has widened from 18.4 percent in 2008.
Former Swiss presidents and government ministers Ruth Dreifus and Micheline Calmy-Rey are among more than 3,760 people who have signed a manifesto calling for pay equity in the country.
Supporters of the manifesto, put online on Sunday, are seeking a stricter application of “equal pay for work of equal value” that was inscribed in the Swiss constitution back in 1981.
They are also seeking a higher representation of women in the boardroom of companies operating in Switzerland.
The mountain country falls well behind Slovenia, which with a 3.2 percent pay gap has the best record in the EU, ahead of Malta (5.1 percent), Poland (6.4 percent), Italy (7.3 percent) and Croatia (7.4 percent).
The difference in pay in Switzerland is roughly on par with that in Spain (19.3 percent) and the UK (19.7 percent) but is smaller than its biggest trading partner Germany (21.6 percent).
The widest pay gap was recorded in Estonia (29.9 percent), followed by Austria (23 percent).
Switzerland scores better for the percentage of employed working-age women, which at 76.6 percent is just below levels in Sweden (77.2 percent) and Norway (77.1 percent), the countries with the highest rates.
However, more than 62 percent of Swiss working women had part-time jobs, Eurostat said.
Related: The International Labour Organization in Geneva is holding a panel discussion on Friday about the "future of women at work". For more information, check here.