An ecumenical movement has come out against Sunday shopping in train stations and airports, the subject of a nationwide vote on November 27.
Catholics and Protestants alike say the measure, if approved, would sound the death knell for family life and would pave the way for extending opening hours across the country.
Wolfgang Bürgstein, general secretary of the Catholic Church's advisory commission, Justitia et Pax, said that Sunday workers were the big losers in the equation.
"Those who have to work more will be missed by their families and by church, religious and social communities," Bürgstein said at a news conference.
Under the changes, shops in major railway stations and airports with sales of more than SFr20 million ($15.5 million) would be allowed to open on Sunday.
The committee's president, Peter Oberholzer, said that the plans displayed politics' penchant for introducing measures by stealth.
"First they introduced working on Sundays in shops located in rail stations; now there are plans in the pipeline for making the whole of Switzerland a train station," he said.
There was also concern that extending Sunday trading would result in deteriorating working conditions for those who were already badly paid and treated.
Ursula Angst-Vonwiller of the Swiss Evangelical Women's Association added that supporting the plans was tantamount to supporting the likes of large retail chains and distributors to the detriment of smaller local and regional shops.
The ecumenical committee represents a wide array of Christian groups. It includes Catholic and Protestant parishes and priests, and is supported by the Protestant Party, the country's sixth largest political force.
Switzerland's churches announced earlier this month that they were against the proposed changes to employment legislation.
swissinfo with agencies
In January a coalition of trade unions, consumer organisations, shopkeepers and churches handed in more than 80,000 signatures to the federal authorities to try to overturn a decision by parliament last September to ease rules on Sunday trading.
At present, only seven railway stations offer Sunday shopping.
Work-free Sundays are considered a major historical achievement by Swiss unions. Sunday working was banned in principle in factories as part of labour legislation in 1877.
The Swiss Federation of Trade Unions has taken a strong line on the issue, arguing that parliament's decision is the first step towards a seven-day working week.
The issue goes to a nationwide vote on November 27.