Churches and social groups argue that Sunday closing offers a respite from commerce and promotes social cohesion.
Retailers say that these days people shop online on Sundays anyway, so trade is taking place regardless.
These orders are often being fulfilled from Poland, says Nils Busch-Petersen, the head of the Berlin-Brandenburg Retail Association.
“There are thousands and thousands of employees directly behind the Polish border, working every Sunday to keep the German illusion of a free Sunday,” he says.
Retailers also argue that Sunday shopping has become a leisure activity, so it should be on the same footing as other ways people might spend their day off.
According to Weber, when KaDeWe is occasionally allowed to open on Sunday, its biggest rivals are “the Italian restaurant where you’re going with your family or the stadium you’re going to for a football match”.
“It’s the museum, it’s the cinema, it’s streaming, it’s online shopping, it’s just staying at home. These are our real competitors in terms of time and experience, and we’re not given equal treatment.”
The trade unions are opposed. They warn that relaxing Sunday trading will put employees at risk of being forced to work unsociable hours.
Retailers counter that Germany’s labour laws, which are stronger than Britain’s, ensure that staff working on a Sunday are paid extra and earn time in lieu.
Weber says that on the 10 Sundays a year when his Berlin department store can open, he has more staff volunteers than he needs.
Smaller businesses are less enthusiastic.
‘Put it in the hands of the retailers’
“We have trouble finding employees who are willing to work every Saturday, so how could we find employees for a Sunday?” says Catrin Schulz, a Berlin optician.
“Also, none of our customers have ever asked for it. We wouldn’t have any benefit if we kept our shop open.”
Busch-Petersen says nobody is suggesting shops should be forced to open. He characterises Sunday trading as a three-way pact between the business owner, the employees and the staff.
“If just one of that trio doesn’t want it, there will be no open store. But if all three want it, why shouldn’t they come together on Sunday?” he says.
For him, this is emblematic of a much wider issue. “The question is whether you need to forbid opening to those who want it. It’s a basic societal question: does the state regulate everything or do you let these things regulate themselves?”
Weber agrees: “I’m not suggesting let’s open on 52 Sundays. I’m saying, put it in the hands of the retailers, because they know their business best.”
For Merz, the question is economic. Consumer confidence has been in the doldrums since the post-Covid cost of living crisis. Apart from an increase in May, retail sales have been sluggish for more than a year.