LONDON (Reuters) - Britain should cut a salary threshold for migrants to 25,600 pounds a year to help fill jobs after Brexit, a government commissioned report said, while warning a planned overhaul of the immigration system could hit economic growth.

FILE PHOTO: UK Border control is seen in Terminal 2 at Heathrow Airport in London June 4, 2014. REUTERS/Neil Hall

With Britain leaving the European Union on Friday, the government is introducing the biggest shake-up of its border controls in decades, ending the priority given to migrants from the bloc over those from other countries.

The proposed changes would make it harder for EU nationals to work in Britain after Brexit while benefiting those outside the bloc by lowering the amount they have to earn.

The Migration Advisory Committee (MAC), an independent body which gives the government advice, recommended lowering the minimum general salary threshold for skilled migrants by 4,400 pounds a year from 30,000 pounds.

“Our recommendations are likely to reduce future growth of the UK population and economy compared to freedom of movement, by using skill and salary thresholds,” MAC chairman Alan Manning said.

“No perfect system exists and there are unavoidable difficult trade-offs,” he added in a statement.

The recommendations are intended to help guide Prime Minister Boris Johnson’s new immigration policy, which will be implemented from the start of next year.

Johnson’s spokesman said the government would carefully consider the report before setting out more details of its new system.

“The government will introduce a firmer and fairer points-based immigration system from 2021 that welcomes talent from around the world while reducing low-skilled migrants and bringing overall numbers down,” he said.

The MAC was tasked with drawing up new salary thresholds for migrants and devising a points-based immigration system, based on that used in Australia, to be put into place once freedom of movement for EU nationals ends.

If the government wanted to bring in a points-based system, then it should also allow a route for skilled workers who did not have a job offer, the committee said.

There should be different minimum salary requirements for certain highly paid professions, the report said. Teachers and healthcare workers should benefit from lower salary thresholds based on national pay scales, it added.

Manning said the proposals would lead to a very small increase in GDP per capita and productivity, and slightly improved public finances.

But while demands on the state-run health service, schools and housing would slightly ease, there would be increased pressures on social care.

For highly skilled migrants - those described as having exceptional talents such as musicians and scientists - the advisers recommend a more open system, saying the current cap on visas is too restrictive.