In September, I warned in a Guardian opinion article that the Brexit process could have the effect of allowing the UK government to bring in more draconian and discriminatory immigration laws, harking back to the 70s and 80s.

Many people wondered how this would happen and the answer was that Brexit would allow the sweeping away of advances like the abolition of the hated primary purpose immigration rule made illegal by the European court of justice.

But now a far more profound and deliberate line of attack is being adopted by the British government in its national immigration policy, under cover of implementing the EU’s General Data Protection Regulation (GDPR), one of the biggest modernisations of data protection law anywhere in the world. Simply put, a new clause in the government’s data protection bill, which implements the GDPR, would remove the rights of people who are subject to an immigration procedure to know what public authorities hold about them and to rectify or delete erroneous or unlawfully collected personal data.

The UK government is acting under the cover of the complexity of data protection law and the chaotic Brexit negotiations

It would affect individuals who are not UK nationals, including nationals of EU member states resident in the UK.

This is an alarming development and anyone who understands immigration law or data protection will realise that this makes it impossible for individuals involved in immigration disputes to obtain their personal information from the Home Office, something which is essential to any administrative dispute. In addition, these measures would also potentially affect the 3 million EU citizens who will soon face new processes to register their residence after Brexit.

We know the deliberate intent of the government here, because similar blanket exemptions have been attempted before but rejected by the House of Commons as far back as 1983. The then home secretary Leon Brittan wanted to make immigration control “a legitimate category for exemption”.

It was roundly condemned in parliament at a time when discriminatory immigration rules were otherwise accepted.

The discriminatory situation being created is being seen with great concern in the European parliament. The UK data protection authority and digital rights organisations are sounding the alarm because of how this measure would disproportionately interfere with the fundamental rights of non-nationals resident in the UK. This would mean that the UK would not uphold the adequate levels of protection required for the exchange of personal data between the UK and other EU states.

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Not only do these proposals stand to flout the important fundamental rights protections of millions of individuals, in the process undermining the already low level of trust of EU citizens in the UK with regard to their rights, they would also lower the UK’s chances of obtaining an adequacy arrangement with the EU. This would also make it harder for the UK to continue to obtain information from several EU information systems, in particular those related to immigration, because of the lack of adequate protection.

If the UK fails to obtain an adequacy arrangement from the EU, it would lose free access to data from nations such as the US, which has negotiated an agreement with the EU called the EU–US Privacy Shield. This would have major real-world economic and commercial impact on the UK.

So, in essence, what is happening here is that the UK government, under the cover of the complexity of data protection law in particular, and its chaotic Brexit negotiations in general, is seeking to create damaging new discriminatory national immigration restrictions. In addition, the government is undermining the implementation of the most important piece of EU data protection law ever drafted, which will have the knock-on effect of undermining the ability of the UK to ensure the free flow of data post-Brexit. This, as people will have seen this week, could have major economic and security implications for the UK.

This issue should alarm all those who care about human rights, a fair immigration system, and a professional and transparent implementation of data protection rules in the UK.

• Claude Moraes is a Labour MEP, representing London. He chairs the European parliament’s civil liberties, justice and home affairs committee