This is a vital cause for farmers and growers, many of whom have senior staff from EU countries who are crucial to the running of their businesses. Since the Brexit vote, these staff have been living with uncertainty about whether or not they will be allowed to stay and work on UK farms.

The “Write to Remain” movement launched a website to help people email Mrs May and press her for an explicit commitment on the rights of European nationals living in Britain and UK nationals living in other member states at the prime minister’s first Brussels summit.

Mrs May has only said that she hopes to guarantee the rights of EU citizens as long as the rights of UK citizens in the rest of the EU are protected.

Her trade secretary, Liam Fox, has come in for criticism for suggesting that the fate of EU citizens in the UK is one of the main cards held by Britain in its negotiations in a sign they could be treated as bargaining chips.

The campaign, backed by leading politicians such as Labour MP Chuka Umunna, trade unionists, a moderate Tory pressure group, business people and think tanks, said the prime minister should honour the commitment made by the official Vote Leave group during the referendum campaign that all EU citizens currently resident in the UK would be allowed to stay.

Organised by two groups, Open Britain and CommonGround, “Write To Remain” calls on Mrs May to “show that neither EU nationals here nor Brits living on the continent are second class citizens who will be used as pawns in the upcoming Brexit negotiations.”

Mr Umunna, a leading supporter of Open Britain, which campaigns to keep the UK in the single market, said: “EU nationals here and Brits living in the rest of the EU are people, not pawns to be used in Brexit negotiations,” he said. According to the government there are about 70,000 seasonal and casual workers in agriculture. The UK apples and pears sector needs an estimated 12,000 seasonal workers a year. Nearly all of these, of course, are EU nationals.

Nick Clegg, the former Liberal Democrat leader, has written an interesting and thought provoking document called “Food, Drink and Brexit.” Whatever your political persuasion, it’s worth reading. Mr Clegg is surely right to point out that: “Many producers rely on EU workers, either for seasonal agricultural work (e.g. fruit picking) or for factory based processing work. It may be harder to recruit such labour in future, both because of expected new restrictions on migration, and falling wages (as a consequence of the collapse of the pound).”

With so much at stake, we urge our readers to use the “Write to Remain” website and put pressure on Mrs May to make a commitment on this imporant issue.