Nearly one in five enquiries made by EU nationals to a free legal advice service for Europeans last year concerned issues relating to the UK, a report has revealed.

The findings, published by the European Citizen Action Service (ECAS), an NGO that provides advice from 60 legal experts through a service called Your Europe Advice, show that enquiries concerning Britain made up 18 per cent of legal queries raised in 2016.

Of a total of 20,491, the number of enquiries about the UK stood at more than 3,500, while Germany and France stood in second and third place, with between 2,500 and 3,000 each. The countries that were the subject of the least queries were Liechtenstein, Iceland, Lithuania and Estonia — all of which had less than 10.

The most prominent topics of enquiry were residence and family rights, with 1,816, entry procedures, with 1,691, and social security, with 1,387, according to the report.

The study, which was presented by ECAS at a conference in Brussels on Wednesday, noted that problems had been reported in the UK, particularly regarding family members of British citizens seeking to live in the UK after residing in another Member State under the CJEU’s Surinder Singh ruling.

It added that the reason for such a high number of enquiries received concerning the UK was “partly due to Brexit”.

Zuzana Pundova, EU rights manager at European Citizen Action Service, which runs the legal advice service, said they had seen a marked rise in the number of EU nationals seeking advice on issues surrounding PR in the UK, as well as similar queries from UK citizens living in EU member states.

She told The Independent: “There has been a rise in the number of queries we’re getting about EU nationals getting permanent residency in the UK since Brexit. The problems are usually connected with delays, so the Home Office delays the decision. The usual time when they should issue a decision is six months, but they are often taking longer. That’s the number one issue.

“We’ve seen a rise in the number of EU citizens asking how they can apply for permanent residency. These are people who have been living in the UK for the required five years, or even much longer. But they’re only now starting to think about how to get a permanent residency.

“There are also more UK citizens living in other member states having problems when applying for permanent residency. In some cases member states are saying they are not entitled to residency, as they won’t be part of the EU. This is a new issue, and it is definitely connected with Brexit.“

Responding to the rise, Nicolas Hatton, founder of The 3 Million, a UK-based group campaigning for the rights of EU nationals, told The Independent: “Many EU citizens living in the UK have been feeling anxious since the referendum due to the uncertainty about their future post Brexit so it’s no surprise that nearly one in five enquiries to ECAS, an European free legal service, originated from EU citizens living in the UK.

"Despite the reassurance from the Home Office that nothing has changed, no guarantees have been granted and we are campaigning for the UK and the EU to guarantee citizens’ rights fully, early and permanently in the Brexit negotiations.”

The findings come days after the European Parliament’s chief Brexit negotiator Guy Verhofstadt called on Theresa May to be "open" to a plan helping British people who want to retain EU citizenship after the UK leaves, saying he wants the European Union to make a “generous” offer to people in the UK angry at losing EU privileges.

An analysis by right-wing think thank Migration Watch meanwhile claimed highly skilled British people could work in the European Union after Brexit under an expanded visa scheme, saying the proposed expansion of the “Blue Card” scheme could provide opportunities for British nationals to work in the EU without any special agreement.

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But Migration Watch added that the scheme is currently “far from complete”, with a reported 87 per cent of Blue Cards issued by Germany alone.

The scheme, which is modelled on the United States’ green card programme, aims to give highly qualified workers from outside the EU the right to live and work in a member state provided they meet specific conditions.