Immigration has become a significant issue in the lead up to the referendum on 23 June. Nobody can say with any certainty what business immigration UK policies would replace the current system if Britain parted ways with the EU.

Proponents of remaining in the EU suggest that EU migrants are net contributors to the economy and promote cultural diversity.

On the other hand, Vote Leave advocates are critical of the strain placed on public services, the inability to cap immigration numbers and the alleged dilution of British wages.

But no-one can tell us what precisely will happen to business immigration if Britain leaves.

Which UK employers will be affected by Brexit?

In 2014, about three million citizens of EU countries lived in the UK. There were about 1.2 million British citizens living in EU countries in 2015.

Many business sectors across the UK have a significant EU workforce, particularly the hospitality, farming, construction, manufacturing, energy and transport industries.

These businesses are desperate to know how the proposed Brexit will affect them.

A long wait for answers

Simply detailing what the new rules will be is not as easy as it sounds.

Article 50 of the Lisbon Treaty permits any member state to withdraw from the EU.

When a state formally declares that it wants to leave, it must then negotiate the terms of the departure with the other states of the EU.

These extensive negotiations would need to cover all aspects of immigration, as well as trade tariffs, financial regulations and a myriad of other significant issues.

All agreements need to be ratified by both the European Council and Parliament.

At the same time, Britain will need to negotiate separate trading arrangements with all non-EU countries.

The Lisbon Treaty allows a period of up to two years to conclude these complex negotiations, which may be extended by unanimous vote of the EU.

During that time, the UK would remain as part of the EU.

The possible outcomes of Brexit on business immigration UK policy 

The Freedom of Movement Act permits EU citizens to migrate freely in any EU country.

If the UK leaves, it could freely limit the migration of EU citizens.

Last week, the Oxford University’s Migration Observatory reported that 75% of EU workers presently working in the UK would not meet the current Tier 2 General visa criteria that apply to migrant workers outside of the EU.

This vast majority are either working insufficiently skilled roles and/or do not earn more than £20,800.

The Vote Leave camp is seeking a flexible migration policy that allows British employers to bring in talent while ensuring control of UK borders. This could look like the Australian or Canadian-style point system designed to attract skilled workers, in high demand industries, from a variety of countries.

Of course, if Britain was to leave the EU, this does not necessarily mean a change in immigration policy at all.

If the UK wants to remain part of the EU single market which, many would argue is extremely advantageous, it will likely be required to maintain the free movement of EU citizens.

One possible outcome is that Britain leaves the EU and remains part of the European Economic Area (EEA), committed to the single market and free movement. Norway, Iceland and Liechtenstein all operate in this way.

For existing migrant workers in the UK

Legal experts and politicians on both sides of the debate maintain that existing migrants from the EU are unlikely to be affected.

When immigration policy changes were implemented in the past, they typically applied only to migrants applying after the date of reform.

Most likely, the UK will implement a system that allows existing migrants from the EU to make visa applications for indefinite leave to remain and, where necessary, bridging visas.

If a system such as this were put in place, it is reasonable to anticipate that similar rights would be granted to UK citizens currently living and working elsewhere in the EU.

Again, this is just speculation. There are no guarantees.

Not only are business owners in the dark as to what business immigration UK policies might be implemented, they can’t even predict who might be in charge of negotiating the new arrangements.

David Cameron will not be obliged to stand down if the referendum is successful but the PM has indicated he will resign before the next election in any event and this could be the catalyst.

Some Vote Leave supporters have suggested that, if the referendum were successful, democracy would require that a second referendum or election follow to determine the UK’s response to particular issues.

For UK business owners that rely on EU migrant labour or have UK staff based elsewhere in the EU, the uncertainty of Britain’s future in the EU also means that the future of their business is uncertain.

Many businesses are attempting to cement the residential rights of their employees now.

There has been a recent explosion in the number or EU citizens applying for British citizenshippermanent residence or making enquiries about other visa contingency plans.