THOUSANDS of EU nationals may inadvertently become illegal residents in the UK after Brexit, a report warns.

Domestic abuse victims, children and the elderly are among those at risk of losing their right to remain in Britain despite meeting the required criteria to stay, say experts. This could be because they struggle to provide documentation and complete a registration process, or do not realise they need to apply to continue living in the UK legally.

The potential gap was highlighted in a paper by the Migration Observatory at Oxford University. Its director Madeleine Sumption said: “The Home Office is clearly keen to create a system that is easy and straightforward to use, and most EU citizens should be able to sail through a simplified application process with little difficulty. But for a minority of people, the process will be more difficult.

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“Many of these are already society’s most vulnerable – whether it is because they are socially isolated, have been victims of exploitation, or face personal barriers such as mental health or poverty.

“We know from other Government programmes, such as child benefit, that people often don’t apply for something even when it’s really in their interests to do so.”

Later this year, the Home Office will launch an application system for EU nationals seeking to remain in Britain after Brexit.

Those who have been in the country for five years by the end of 2020 will be able to apply for settled status, meaning they are free to go on living and working in the UK.

People who have arrived by December 31, 2020 but do not have five years’ residence will be able to apply to stay until they have reached the threshold, at which point they can seek settled status.

The Migration Observatory analysis said a “potentially significant” number of individuals may not be aware they can or need to apply. One group in this category are children whose parents do not themselves apply, do not realise their offspring need to or mistakenly believe their UK-born children are automatically UK citizens.

There are more than 900,000 children of non-Irish EU citizen parents living in the UK, born either here or abroad, according to the report. This includes an estimated 239,000 UK-born children whose parents report that they are UK citizens – but the paper says available data suggest tens of thousands may not be.

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Also in this bracket could be 140,000 people who have lived in the UK for more than 30 years, 56,000 people aged 75 or over, and more than 145,000 EU nationals who have already been granted permanent residence but still need to apply for settled status, the study adds.

More than three million EU nationals living in the UK will be able to apply to stay when an online application form goes live towards the end of this year. Applicants will have to provide an ID document and a recent photograph, as well as declare any criminal convictions. The scheme will remain open until the end of June 2021.

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A Home Office spokesman said: “We are well aware of the challenges of ensuring three million EU citizens and their family members living here understand the need to apply and have the ability to.

“That is why we have already launched a national awareness campaign, are holding monthly meetings with EU citizens’ representatives to understand their needs and are planning a range of support for vulnerable groups such as the elderly, children and families, victims of domestic violence and those with English as a second language.

“We will be setting out further details before the summer and EU citizens will have plenty of time to make an application”.