Thomson Reuters Foundation

An immigration scandal which led to the resignation of Britain's home secretary and sparked anger over the treatment of some migrants has reignited another debate - national identity cards.

Home Secretary Amber Rudd quit on Sunday after acknowledging she "inadvertently misled" parliament by denying the government had targets for the number of illegal migrants it deports.

Ministers have struggled for weeks to explain why some descendants of the "Windrush generation", who were invited to Britain from former colonial Caribbean nations to plug labour shortfalls between 1948 and 1971, were denied basic rights.

The issue has put a multi-billion pound identity card scheme back into the spotlight and re-ignited a debate over the amount of documentation required to prove one's identity.

"Biometric cards remain the best way to prove and so protect a citizen's identity, which is why most major European countries have them," former home secretaries Charles Clarke and Alan Johnson wrote in an open letter in "The Times" newspaper.

They said the policy would help cement the status of thousands of undocumented British citizens and was needed to ensure the rights of European Union nationals living in the UK ahead of Brexit next year.

The UK scrapped identity cards in 2011 but still has a biometric residence permit system for foreign nationals looking to stay over six months, or settle permanently, in Britain.

Yet critics argue the system, only a decade old, is not helpful for migrants who came to Britain before then.

"The Windrush generation issues have shown us sometimes, even when a person does have the legal right to be in the UK, they can struggle to prove it when applying for residence documents," said Madeleine Sumption, director of the Migration Observatory at Oxford University.

"Getting an ID card would be dependent on this too – so ID cards would not necessarily solve the problems some Commonwealth migrants have faced in the UK, like access to (health services)," she told the Thomson Reuters Foundation.

Others agree, such as the group NO2ID which has opposed the policy from the start. They said introducing such cards would not resolve the key issue of the amount of documentation legally required to prove one's identity.

Tetiana Bersheda, founder of online legal advice platform LexSnap, said Britain should consider using resources which are currently available, such as electricity bills, as proof of residence, and less expensive tools such as digital databases.

The biometric residence permit card scheme was one of the world's most ambitious biometric projects when launched and raised some eyebrows for the amount of personal data required, including personal details, fingerprints and a facial image.

Other governments have since introduced similar identity systems, like India's national identity Aadhaar project.

In a bid to crackdown on fraudulent documents, the European Commission proposed earlier in April that identity cards held by EU citizens should include digital images of fingerprints.

If the UK does want to reintroduce identity cards, then it should consider online data encryption instead, said James Song, founder and CEO of blockchain technology startup ExsulCoin.

"Printing those cards is very expensive...You have to buy a certain type of machinery, you can't just use any type of card printing technology, and then, inside the card, you have to interweave security measures," he said.

Britain's interior ministry, or Home Office, is known in government as one of the toughest departments to lead, charged with immigration, the police and security at a volatile time.

Prime Minister Theresa May appointed Sajid Javid, the son of immigrants from Pakistan, to the role on Monday to mixed reactions, with analysts saying government officials need to re-examine current policies in place for immigrants.

"Identity cards aren't a way of solving the fundamental issue," said Marley Morris, senior research fellow at the Institute for Public Policy Research, a UK-based think tank.

"There's a need to rethink aspects of the hostile environment policy (towards migrants)...right now it doesn't seem to be reasonable and it's unfair."