Britain is considering measures to restrict immigration for all but the highest-skilled EU workers, a leaked government document said, plans some companies called alarming and an opposition lawmaker described as “plainly cruel”.

Prime Minister Theresa May told parliament that while immigration had been good for the economy, last year’s vote to leave the European Union showed that people wanted to control the flow of people coming into the country.

But companies, especially those in the catering, social care and retail industries which depend on the steady stream of workers from abroad, say they fear a restrictive immigration policy will leave them unable to hire the staff they need.

In the document, leaked to the Guardian newspaper and marked “draft – official sensitive”, the interior ministry said Britain was changing its focus to make sure, where possible, British companies take on British workers rather than migrants.

“Put plainly, this means that, to be considered valuable to the country as a whole, immigration should benefit not just the migrants themselves but also make existing residents better off,” the document said.

A ministry spokesman said the government did not comment on leaked draft documents and would set out its initial proposals on immigration controls later in the year.

May, who as interior minister was in control of migration for six years before becoming prime minister, said the flow of migrants must be controlled to ease the pressure on public services such as schools and hospitals, and to protect those hardest hit at “the lower end of the income scale”.

Net migration, which the latest figures put at 246,000, is still far higher than what May describes as “a sustainable level”.