MPs have serious concerns about the scheme by which EU citizens must apply to stay in the UK after Brexit, and fear it will lead to a new Windrush scandal.
A report examining the EU settlement scheme found that "large numbers" of the 3.8 million EU nationals resident in the UK could be left in limbo or ruled to be in the UK illegally.
An overhaul of the scheme is recommended, so that European citizens who are vulnerable or who have lived in the UK for decades have their rights guaranteed and do not have to apply for their right to stay.
MPs on the Home Affairs Select Committee, examining the scheme in detail for the first time since it fully launched at the end of March, accused Home Secretary Said Javid of taking a "callous" attitude to enforcing the rules.
Under the current scheme, EU nationals who can prove they have lived in the UK for five years can apply for settled status, through a government app. Those who have lived here for less than five years can apply for pre-settled status.
Committee chairwoman Yvette Cooper said: "The government's current plans for the EU Settlement Scheme show they are not learning the lessons from the Windrush scandal.
"The problems faced by the Windrush generation showed how easily individuals can fall through gaps in the system through no fault of their own and how easily lives can be destroyed if the government gets this wrong.
"Too many people could be missed out under the current plans for the settlement scheme arrangements - including children or the elderly who have lived here many years. The government should enshrine people's rights in law so they are protected rather than putting them at risk from problems with the bureaucratic process."
The Home Office insists that no one has yet been turned down and their intention is to help individuals apply successfully by the end of the proposed transition period on 31 December 2020.
Some £3.75m has been put into a public information campaign to highlight the need to apply, and hundreds of Home Office caseworkers employed to help applicants use the online system.
Mr Javid told the committee in February that the government wished to provide "reassurance and confidence for all the EU citizens that are here in the UK that we not only want them to stay, we want to make it as easy as possible to protect their rights".
But campaigners argued that the government should guarantee the rights of eligible EU citizens to stay in the UK by law, while encouraging them to register for settled status only in order to take up employment or benefits.
The report calls on ministers to take this approach and guarantee citizens' rights after Brexit, with or without a deal. They also warn that the process has been "blighted by technical issues" and is not accessible to "those who may not have an online presence".
The MPs said the home secretary's statement that applicants would be granted the correct status if they were able to demonstrate they qualified for it "strikes us as callous, and rigid enforcement of this line would not be fair or just, as it would allow for the possibility of long-term EU residents of the UK-who, for whatever reason, are unable to evidence their eligibility for settled status-being granted a lesser status than that to which they are rightfully entitled".
People at risk of being left out, according to the report, are 284,000 elderly European citizens resident in the UK for more than 20 years; 400,000 citizens with permanent residency who may be unaware of the need to apply; relatives and children of EU citizens; and isolated individuals such as those in care, or victims of abuse who may not have access to the relevant documentation.
Applicants are asked to prove their identity, declare any criminal convictions and upload a facial photograph. Officials check employment and benefits data to confirm proof of residence and all applications are run through UK criminality and security databases.
A Home Office spokesman said: "We disagree with the Home Affairs Select Committee's assessment of the scheme, which is performing well with more than 600,000 applications received by the end of April and hundreds of thousands of people already being granted status.
"The scheme protects the rights of EU citizens in UK law and gives them a secure digital status which, unlike a physical document, cannot be lost, stolen or tampered with.
"We have taken great care to learn from the experience of the Windrush generation. It's part of the reason why there are 200 assisted digital locations across the UK to help EU citizens apply, dedicated staff in our Settlement Resolution Centre and £9 million available for 57 organisations across the UK to support an estimated 200,000 vulnerable people to apply."