You may have seen in the British press this week that Reform UK has promised to exclude all foreign nationals in the UK from most benefits if the far-right populist party were to come into power.

Nearly all welfare payments - including universal credit, housing benefits, pension credit, jobseeker's allowance, child benefits, free childcare, and disability benefits - would become inaccessible to non-British nationals residing in the UK, Reform says, an overhaul they claim would save the UK taxpayer £21 billion a year by 2029.

Reform’s promised benefits crackdown would apply to all foreign nationals, including European Union citizens with settled status in the UK.

Limited exceptions would apply for service in the armed forces and contributory state pensions for individuals who have paid into the system.

"The welfare state is there for Britain. No British citizenship, no entitlement," Robert Jenrick, Reform's economics spokesperson, said on Monday.

On top of the grave consequences such a ban could potentially have for many of the 13 million foreign nationals who live in the UK, some sources are suggesting Brits living across Europe - including those in Spain - would also be impacted.

The argument is that Reform UK’s proposed ban would breach the Withdrawal Agreement (WA), more specifically the equivalent and protected rights it grants both EU and UK nationals residing on either side before Brexit.

This may well force Brussels to scrap the WA and redraw it again, and it has been suggested in the British press that the EU could retaliate with a tit-for-tat welfare ban on Brits living in Europe.

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That suggestion is being pushed by Reform UK itself, who has said they’d set aside £500 million for returning British citizens who had their benefits withdrawn in their EU country of residency.

Speaking on BBC Breakfast, Reform’s Danny Kruger said: "So I'd understand if the Europeans decided to apply the same principle that we are and to deny our nationals access to their welfare system and we will pay for that ourselves."

A spokesperson for the governing Labour Party also said that "these plans would mean ripping up the UK’s Withdrawal Agreement with the EU, plunging the UK back into years of Brexit renegotiations."

Although all this hinges on a potential election win by Reform in the next UK general election in 2029, and whether Farage’s party follow through on their promises, would the EU really turn its back on its resident British population?

Lisa Burton, Vice Chair of Bremain in Spain, one of the chief advocacy groups campaigning for Britons in Europe and the UK rejoining, told The Local Spain that such a reaction from Brussels seems unlikely.

"Whilst we are deeply concerned about the rights and wellbeing of our fellow EU citizens in the UK, the reporting and talk of ‘retaliation’ by the EU toward British migrants living here is one that is likely not justified," Burton argued.

"The EU would not retaliate by withdrawing benefits from UK citizens living in the EU because not only would such a move be entirely contrary to the EU’s ethos, but it is also explicitly prohibited by the Withdrawal Agreement.

"The EU would therefore follow due process, and a far more likely response would be legal action against the UK, potentially involving fines or other proportionate measures, including trade-related action," the Bremain in Spain representative added.

For Nigel Aston, head of Eurocitizens (another advocacy group for Brits in Spain), Reform's policy is "deeply worrying".

"To my mind any action of the type suggested would essentially be a breach of an international agreement and that could lead to counter measures," Aston told The Local, adding that "all this is speculative without Reform forming a government."

The Eurocitizens spokesperson didn't rule out that individual EU Member States could seek to retaliate against Reform's policies, but ultimately believed the European Commission could strike down such reprisals.

The EU has not issued an official response to Reform UK’s welfare proposal. As Farage's party is an opposition party and not the sitting UK government, Brussels rarely provides formal statements on their policy announcements.

Around 1.3 million British citizens live across the remaining 27 member states of the European Union, according to the UK Office of National Statistics. Eurostat puts the figure closer to 800,000.

Spain is widely considered to have the biggest British population in the EU, but again the figures vary depending on the source (residency documents, town hall registration etc), with a population bracket of between 280,000 and 420,000.

In Spain, around 80 to 83 percent of those receiving major social benefits are Spanish nationals.

READ ALSO: Which benefits will Spain's 'regularised' migrants receive?

That’s not to say that there aren’t UK nationals who do enjoy the benefits of Spain’s robust welfare system, but there aren’t official figures to give us an idea.

Given that the majority of Brits in Spain are retirees, it’s the country’s much respected public healthcare system that they arguably benefit from the most.

Brits protected under the Withdrawal Agreement in Spain have access to the same social security rights, healthcare, unemployment benefits and pensions as a citizen of the European Union, under conditions of full equality and non-discrimination with respect to Spaniards.

Britons who’ve arrived after Brexit can also contribute to the social security pot in return for access to the welfare system.

It’s hard to envision that the Spanish government - even if a more PP-Vox coalition were to come into power - would seek to punish the country’s British residents to get back at a Reform-led UK.

During Brexit talks, Spanish Premier Pedro Sánchez defended the reciprocal protection of the rights of British citizens in Spain and Spaniards in the United Kingdom in the face of different Brexit scenarios, even saying he’d offer residency to all 400,000 Brits in Spain in the event of a ‘hard’ Brexit.

"This is yet more sabre-rattling by Reform UK, announcing another fantasy policy designed to create a wedge issue and demonise migrants," Bremain in Spain's Burton added.

"However, that reality does not stop people from feeling fearful and anxious about their futures, and I'm sure it will bring back uncomfortable memories and feelings for many, because since the Brexit referendum in 2016, successive UK governments have used our fellow EU migrants and us as political footballs, and sadly, it seems this is still the case, even with our legal protections."