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It was the central issue of the 2016 EU referendum, and now nearly four years later one of the leaders of the Brexit campaign has finally set out how the UK will “take back control” of its borders.

Priti Patel, the home secretary, has announced it will be much harder for EU citizens to come to the UK after the Brexit transition but easier for immigrants from outside Europe.

The new points-based system will end the free movement of EU citizens and bring overall immigration numbers down, she said.

But who will be coming here once the Brexit transition ends in December, how will they qualify, and will it hurt the UK’s economy?

The key questions are answered here:

What’s happening?

Broadly speaking, EU citizens will no longer be able to enjoy free movement into the UK and will have to get a visa under the same immigration rules as non-EU migrants if they want to work or study here.

This means there is no route at all for low-skilled immigration from anywhere in the world, apart from seasonal agricultural workers, and this essentially amounts to a massive tightening up of the rules for EU citizens.

But at the same time Patel is relaxing the rules for skilled migrants to come into the UK, which will make it easier for people to come from places like India, Australia or Canada.

This includes lowering the minimum salary required from £30,000 to £25,600, and lowering what counts as “skilled” from a graduate-level to an A-level qualified job.

Alongside the traditional “skilled” jobs, lowering the skill threshold will open the UK up to the likes of painters, decorators, tilers, carpenters, joiners, plasterers, glaziers, window fitters and child minders from outside the EU.

EU citizens with similar medium-skilled jobs will also be able to come, but the likes of labourers, waiters, waitresses and baristas that have come from Europe in the past will be barred from Britain.

Will it lead to less immigration and will it hurt the economy?

The independent Migration Advisory Committee (MAC) report into a points-based system found that 70% of EU citizens who arrived under free movement since 2004 would be ineligible under the new rules.

This would mean the number of Europeans coming to Britain would be reduced by tens of thousands.

But the corresponding relaxing of rules for non-EU migrants means more are likely to come.

Patel said the new system will “bring overall migration numbers down” while attracting “the brightest and the best”.

But the Migration Advisory Committee (MAC) estimated a system very close to what the government is following closely would cut economic growth, immigration and the total population.

It will have essentially “zero” impact on employment opportunities and wages for British workers, and GDP per capita would only rise because the mix of people in the economy was changing.

The changes will also reduce pressure on the NHS, schools and social housing, but increase pressure on social care and increase the ratio of dependent children and elderly people to workers.

How will it work?

Potential immigrants will have to score 70 points on a system devised by the Home Office to allow more skilled workers into the UK, while keeping out low-skilled migrants. 

Each prospective migrant must have three things which automatically add up to 50 points – a job offer from an approved sponsor, a job at the appropriate skill level, and the ability to speak English.

They can then earn the extra 20 points through one or a combination of “tradeable” characteristics, such as having a high enough salary, having a PhD (with more points for science, technology, engineering or maths subjects), or having a job in a shortage occupation.

The table below sets out the details of how points are allocated.

This is just the first stage and the Home Office hopes to add more characteristics that earn tradeable points in the future, for example qualification levels, age or experience.

Is that the only way working immigrants can come here?

No. Tourists will still be able to come from the EU for six months without a visa.

The most highly skilled workers from the EU will be able to come on global talent visas without a job offer in the same way that currently applies to non-EU workers. 

The pilot scheme for seasonal workers in agriculture will also be quadrupled to 10,000 places.

Deals with eight countries around the world also allow 20,000 young people to come to the UK every year. 

And students will be able to come to Britain if they have an offer from a university or other approved institution, speak English, and can support themselves during their studies.

They will also benefit from a two year post-study work visa during which graduates will be able to stay in Britain and do what they want. 

There are also a range of other routes into the UK for specialists such as innovators, ministers of religion, sportspeople, artists and musicians and so on.

Patel in October also introduced a “vindaloo visa”, aimed at fulfilling Vote Leave’s promise during the 2016 EU referendum that Brexit would allow more Asian curry chefs to come to the UK.

What will EU migrants need to do to get a visa?

EU migrants will now have to submit facial biometric data using their smartphones, and fingerprints may eventually be required.

Non-EU citizens will submit their biometrics at a visa application centre, as they do now.

All immigrants will also have to pay for their visas, something which does not apply to EU citizens currently. 

But EU citizens will be able to continue using e-gates, although the UK may revoke these rights in the future.

What’s the reaction been like?

Shadow home secretary Diane Abbott backed MAC’s assessment that this is not actually points-based but a salary threshold system and said there would need to be “so many exemptions” for the NHS, social care and businesses “that it will be meaningless”.

“Ultimately, it will also be very difficult to attract the workers we need at all skill levels while the Tories’ hostile environment is in place,” Abbott added.

Christina McAnea, assistant general secretary of the Unison union, said the plans would be a “disaster” for the social care sector.

“Companies and councils can’t recruit enough staff from the UK so have to rely on care workers from elsewhere. But even with these migrant employees, there’s still way too few care workers to meet demand,” she said.

“Care work is highly skilled, but low paid, so falls foul of the government’s arbitrary immigration threshold.

“Suddenly ending this desperately needed supply of labour will cause huge problems across the country. The government simply has to think again.”