A former head of the civil service has called for an investigation into who authorised the destruction of thousands of landing cards of Windrush migrants.
Lord Kerslake told BBC Newsnight the Borders Agency was effectively part of the civil service and took its advice from ministers.
Theresa May has said the decision was taken under Labour in 2009.
But Labour has disputed this, saying the Home Office had earlier said the decision was taken in 2010.
The Windrush row erupted after it emerged that some children of Caribbean migrants who settled in the UK from the late 1940s to the 1970s had been declared illegal immigrants and threatened with deportation.
A Home Office task force set up in response to the outcry is now looking at 113 cases as a result of calls to a new hotline.
Lord Kerslake said it was "pretty unlikely" that the Home Office would destroy records, as "quite a lot of care" was taken on these things.
"But the truth is we don't know," he said.
"We need to investigate this in more detail to understand what happened.
"What we can say is that the Borders Agency was effectively part of the civil service and it took its advice and direction from ministers."
Lord Kerslake, who has been advising Jeremy Corbyn, said some ministers were "deeply unhappy" about the introduction of the strategy to create a "hostile environment" for illegal immigrants under then home secretary, Mrs May.
He described Mrs May's approach to illegal immigration as "almost reminiscent of Nazi Germany in the way it's working".
On Wednesday, Mrs May apologised again for the distress caused to anyone told they must leave the UK.
Landing cards were filled in by Commonwealth citizens arriving from the West Indies and elsewhere, and were used by officials to help subsequent generations prove they had a right to remain in the UK.
They had been stored in a basement for decades but Downing Street says the UK Border Agency approved a business case in June 2009 to dispose of paper records, including the cards.
The decision to destroy the cards themselves was taken in October 2010, after the coalition came to power. Mrs May was not involved in the decision, which was taken at official level, said No 10.
'I feel like I have been deported'
Jamaican national Clayton Barnes arrived in the UK about 1959 and stayed for 51 years.
Had indefinite leave to remain, but unwittingly forfeited that when he retired to Jamaica.
He found he could not get back into the UK, even to visit his family and despite having a UK pension.
"[I feel] horrible. Right cut up because I'd been here all these years and worked for my pension… income tax, everything. Worked hard… And now this," he told BBC Newsnight.
When asked if he felt like he had been deported, he said: "Yes. Why can't I come back? I'd like to come back and see my family."
His daughter Samantha Barnes-Garner said the problem started in 2013, when she booked flights for her father to return to the UK and he was told at check-in that his indefinite leave to remain was invalid.
"He was absolutely devastated," she said.
"He could barely talk on the phone to me. He felt that he'd done something wrong.
"It does feel like he's been deported because he's not allowed back."
- 'I'm an Englishman': Windrush stories
Downing Street said new information was coming to light about the handling of the landing cards all the time, which was why there was a discrepancy between information given out on Tuesday and Wednesday.
But a Labour Party spokesman said the government's story was "shifting by the hour".
"First Downing Street claimed the decision to destroy the Windrush-era landing cards was made by the Home Office in 2010 for data protection reasons. Then the Home Office passed the buck to a 2010 decision by the UK Border Agency.
"At PMQs, the prime minister tried to shift the blame on to the last Labour government but was undermined by her own spokesperson minutes later, who then stated it was an operational decision, which Labour ministers would not have been aware of. Her spokesperson couldn't even say when the cards were destroyed."
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