Switzerland's churches have come out against a plan to keep shops open on Sundays in major airports and stations throughout the country.
They say the proposal, which goes to a nationwide vote on November 27, would affect families most and threaten social cohesion.
"Accepting the extension of opening hours for shops in airports and stations would be the first step towards abolishing Sunday's special status," said Thomas Wipf, president of the Swiss Federation of Protestant Churches, on Tuesday in Bern.
Wipf warned that the Senate was already considering the extension of Sunday trading. "Swiss labour legislation could undergo fundamental and decisive changes," he added.
For the Catholic and Protestant Churches, Sundays help cement the community, giving people time to spend with their families, friends, God, on the sports field or on cultural activities.
"If people have to work on Sunday, our society will lose its 'warmth'," said Wipf. "We will notice the absence of others."
Speaking on behalf of the Catholic Bishops' Conference, Pierre Bürcher, auxiliary bishop in the diocese of Lausanne, Geneva and Fribourg, added that people should be allowed to practise their religion.
"The ban on Sunday work gives churches a space of their own," he noted. "And it gives workers the possibility to participate in religious ceremonies."
Bürcher and Wipf said they were not opposed to some shops being open on Sundays, as allowed under current legislation, but want it to remain the exception rather than the rule.
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.
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. At present, only seven railway stations offer Sunday shopping.
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.
Work-free Sundays are considered a major historical achievement by Swiss unions. Sunday work was banned in principle in factories as part of labour legislation in 1877.
swissinfo with agencies
Last year, parliament approved an extension of Sunday trading hours in major airports and stations across the country.
Until now, Sunday trading has been severely restricted in Switzerland.
The Swiss Federation of Trade Unions, the Unia union and the Catholic and Protestant churches joined forces to fight this change to Swiss labour legislation.
The issue goes to a nationwide vote on November 27.