British firms struggling to fill low-skilled jobs should be training British workers to plug the gaps rather than relying on immigration, Theresa May has said.

A cabinet rift over the lack of provision for low-skilled labour in a future immigration policy is believed to be among the reasons for an apparent delay in the publication of the immigration white paper.

The chancellor, Philip Hammond, and the business secretary, Greg Clark, have both argued for looser restrictions on low-skilled foreign workers, with business complaining they cannot fill positions.

Speaking at the G20 summit in Buenos Aires, May was clear she would not be moved from the recommendations of the migration advisory committee (MAC), which advocated a clampdown on low-skilled workers.

“What I’d say to business is we have seen a huge creation, a significant creation of new jobs in our country,” May said. “We’ve also seen, from work that the government is doing, our encouragement of people into the workplace.

“What I hope to see and what I’m sure we will be seeing is opportunities for young people in the UK, opportunities for training and skilling young people in the UK.”

Experts have said the MAC recommendations would effectively end low-skilled migration and would be the biggest change to the UK labour market in a generation.

Carolyn Fairbairn, the director of the CBI, has said the changes would affect businesses from housebuilders to healthcare providers. “The best way to build public confidence is through a migration system based on contribution, not numbers,” she has said.

May said there was no date set for the white paper’s publication but strongly suggested there would be no softening of its proposals.

“The MAC report was very clear about the way the government should approach this, that this should be a skills-based immigration system for the future, and obviously when we bring the white paper forward, we’ve already said we’ll have a skills-based system,” she said.

The Guardian revealed on Thursday that the government is to relax its immigration rules to let more foreign doctors come to Britain to help tackle the NHS’s widespread shortages of medics.

Ministers have agreed to significantly expand the number of doctors allowed to come to work in Britain under the medical training initiative, from 1,500 a year to as many as 3,000.