Ashdod, on Israel’s southern coast plain, has become the battleground for the future of a new law that could force supermarkets to close on Shabbat.

Demonstrations have been held in the city over recent weeks after its council decided to levy fines on shops that open on Judaism’s day of rest.

The city has become Israel’s sixth largest in recent decades through an influx of new Charedi communities and secular families arriving from the former Soviet Union.

The two groups live in separate neighbourhoods, but Charedi politicians hold sway over the local council and have pressed Mayor Yehiel Lasri to close shopping centres open in the mainly secular areas.

The Knesset narrowly voted earlier this month to pass a Strictly Orthodox bill granting Interior Minister Arye Deri the power to order local authorities to close shops in their area between Friday and Saturday nights.

Mayors in large cities said it would be difficult to enforce, given they could not send Jewish inspectors out on Shabbat to check whether shopkeepers are keeping their businesses open.

Even some Charedi politicians admitted that despite supporting the law in principle, they did not believe it would actually be implemented.

But in Ashdod, city inspectors have been handing out fines to shops that trade on Shabbat.

Politicians who oppose the so-called “Groceries Law” have flocked to Ashdod in the hope of capitalising on the widespread public dislike.

Among them was Defence Minister Avigdor Lieberman, who took the highly irregular step of appearing in public on Shabbat while shopping and drinking coffee, surrounded by Russian-speaking constituents.

The move enraged his Charedi coalition colleagues, but they are aware that the controversy over the new law is a major boost for secular parties – not just Mr Lieberman’s Yisrael Beitenu, but Yair Lapid’s opposition Yesh Atid, which has been rising in the polls.