Supporters of the change argue that it ends the “absurdity” of the current regulations which allow prepared cervelat sausages to be served 24 hours a day at service stations, but not those that are uncooked.

Unprepared food cannot be sold from 1 to 5am daily because of Switzerland’s labour law.

Service stations are allowed to stay open all night to sell fuel and serve coffee and cooked food.

The upper and lower houses of parliament have approved an amendment to the law that would allow articles that “meet the needs of travellers” to be sold 24 hours a day at service stations on motorways and on roads with significant traffic.

But opponents launched a referendum to challenge the proposal.

Those against the change fear it would open the door to a rampant liberalization of opening hours for shops, with more retail workers consequently facing night shifts .

The Liberal party has reduced its argument in a campaign that calls simply for the “legalization” of uncooked sausages.

A poll published on Wednesday by SSR, the Swiss national broadcaster, showed that the voting population remains divided on the issue, to be decided at the polls on September 22nd.

The survey showed that 48 percent of respondents backed the proposed change to the law, while 45 percent were opposed and seven percent were undecided.

A total of 1,406 people were interviewed from across Switzerland between August 30th and September 7th.

Past efforts to change restrictive shopping laws have met with little success in Switzerland, where most shops close on Sundays and late-night shopping is not allowed outside of train stations and airports.