Limiting immigration to the UK government's annual target of 100,000 in the event of a Brexit would have a negative impact on public finances, according to a report commissioned by the Institute and Faculty of Actuaries (IFoA).
Produced by the National Institute of Economic and Social Research, the report found that a cut in net migration by around 150,000 could cost the UK government more than £3bn per year by 2032 in tax revenues and state benefits, and more than £8bn a year by 2057.
The IFoA said these impacts, however, could be mitigated, or even reversed, if the government introduced a skills-based policy such as the points-based system in Australia, with only high-skilled people on high wages allowed in the country.
Derek Cribb, chief executive of the IFoA, said: "A reduction in EU migrants, an increase in total non-EU migrants and an upscaling of immigrant skills are all possible policies which have been aired in the referendum debate."
To offset the funding gap of £8bn in 2057, the report proposed the government could raise the state pension age from 68 to 69.
Alternatively, the amount of state incomes for new pensioners could be lowered by 3.5%, equating to around £300 less per person per year.
Another suggestion was the increase of the rate of national insurance contributions by nearly 1.5%.
Cribb said: "To date, focus has been on either the additional expenditure due to immigration or the additional income it brings in. Our report brings them together to show the overall budgetary impact of these scenarios on the state pension."