If the government wants to implement an Australian-style points-based immigration system, the threshold for skilled workers entering the UK should be cut from £30,000 to £25,600, a report has recommended.
The Migration Advisory Committee (MAC) - which provides independent, evidence-based advice to the government - said past "mistakes" should not be repeated when plans are drawn up.
It said the existing general salary threshold for skilled migrants coming to the UK with a job offer should be brought down by £4,400.
Commissioned by the Home Secretary in June, the report says replacing the current freedom of movement system with skill and salary thresholds is "likely to reduce future growth" of the economy and UK population.
But the report added: "We estimate very small increases in GDP per capita and productivity, slightly improved public finances, slightly reduced pressures on the NHS, schools and on social housing, though slightly increased pressures on social care."
"No perfect system exists and there are unavoidable, difficult trade-offs," said MAC chair, Professor Alan Manning.
The committee urged the Government to make decisions on the UK's future immigration system soon, to give employers "adequate time" to prepare for its introduction in January next year.
Downing Street said it would consider the Migration Advisory Committee's report.
A Number 10 spokesman said: "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.
"We will carefully consider the report before setting out further details on the new system."
Teachers and skilled NHS workers "would continue to benefit from lower salary thresholds", the report recommended, but added a higher threshold should be kept for higher paid occupations.
The points-based system should have options for skilled workers who do not have a job offer so "talented individuals" could register their interest in coming to the UK with monthly invitations to apply, according to the findings.
The news comes after the Prime Minister announced that top scientists, researchers and mathematicians will be given fast-tracked entry to the UK from next month.
Meanwhile, most Britons think nurses, doctors and dentists should score highly under a points-based immigration system to get a UK visa, according to a poll carried out for think tank British Future.
Some 2,305 British adults including 427 people from Scotland, were quizzed between January 10 and 13 on their thoughts about the post-Brexit immigration system plans.