British citizens living in Europe could have their rights cut after Brexit, a leading MEP has warned.

Claude Moraes, the chair of the European Parliament’s civil liberties committee and a member of the parliament’s Brexit steering committee, said that Theresa May’s controversial offer to EU citizens in the UK could be matched by Europe, leading to diminished rights for the 1.2 million UK citizens living on the continent.

The Prime Minister’s proposals would see anyone who has already lived in the UK for five years given a new “settled status”, securing their position in the country. Anyone arriving after the triggering of Article 50, but before a notional cut-off date, yet to be set, would also have the chance to stay for five years and gain the status.

However, the proposals would restrict the right of EU citizens in the UK to bring over family members and also would mean they would lose the protection of the European Court of Justice.

When asked if UK citizens living in Europe would have their rights similarly reduced in return, Mr Moraes said, although a response had not yet been issued by the EU 27, a similar plan should be expected.

“I think it is inevitable if this sticks and there is no upgrading of this offer by Theresa May,” he told The Independent.

“This is often reported as being just about the three million EU citizens in the UK but it is also about the 1.2 million UK citizens in Europe. I don’t know exactly how the EU 27 will respond but one aspect will have to be reciprocity.

“They won’t be able to put the 1.2 million people in the better position than the three million EU citizens in the UK.”

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Mr Moraes also added that he believed Ms May had done this while “in full knowledge that there will be reciprocity”, leaving UK citizens living in Europe worse off.

Critics had already branded Ms May’s offer as “vague” and “not sufficient”, with senior figures in the Brexit negotiations publicly speaking out against her proposal.

European Commission President Jean-Claude Juncker called her offer “a first step, but not sufficient”, while the European Parliament's Brexit co-ordinator Guy Verhofstadt underlined that the offer "does not fully guarantee the rights of EU citizens living in the UK".

He added on Twitter: “Hopefully the UK position paper ... will deliver what we are looking for.”

Leading figures in the UK also criticised Ms May’s offer with both Labour and the Liberal Democrats saying it was not good enough.

Sir Keir Starmer, the Shadow Secretary of State for Exiting the EU, said: “Labour has been clear that people should not be bargaining chips in the Brexit negotiations. The Prime Minister’s offer is too little too late and falls far short of the full and unilateral guarantee Labour would make.

“We believe there must be a clear commitment that there will be no change to the status of EU nationals in the UK. This is not only the right thing to do, but it will also help deliver a reciprocal agreement for the 1.2 million UK nationals living in the EU.”