The prime minister was accused of trying to “cook the books” and a “barefaced lie” over the assertion, made despite figures showing nearly 100,000 migrants still waiting for a decision.
Mr Sunak’s home secretary James Cleverly later said it was “impossible” to forecast how long it would take to deal with the outstanding cases.
The government said it had met Mr Sunak’s pledge to clear all so-called legacy asylum claims – counted as those submitted before June 2022. But official statistics also confirmed that 4,500 of those cases were still ongoing.
Mr Sunak also came under fire for a tweet suggesting the government had cleared the entire backlog – as figures showed a total 98,599 asylum claims still languishing in the system.
On 2 January, Mr Sunak posted on X, formerly Twitter: “I said that this government would clear the backlog of asylum decisions by the end of 2023. That’s exactly what we’ve done.”
In a letter published on Thursday, to Liberal Democrat MP Alistair Carmichael who had raised concerns with the watchdog, Sir Robert said: “The average member of the public is likely to interpret a claim to have ‘cleared a backlog’ – especially when presented without context on social media – as meaning that it has been eliminated entirely, so it is not surprising that the government’s claim has been greeted with scepticism and that some people may feel misled when these ‘hard cases’ remain in the official estimates of the legacy backlog.”
Mr Carmichael, the Lib Dem home affairs spokesman, said Sir Robert’s letter showed once again that Mr Sunak had not cleared the asylum backlog. “Not only is the Conservative government celebrating something that is no achievement, they are twisting the facts – as proven by the UK Statistics Authority just today.
“Thousands of vulnerable people are still living in limbo as they wait for their claims to be processed. The British public deserves better than this.”
Mr Chote went on to say: “There may be a perfectly good case for excluding cases of this type from any commitment to eliminate the backlog over the timeframe the government chose, but this argument was not made at the time the target was announced or when it was clarified in the letter to the home affairs committee.”
He added: “This episode may affect public trust when the government sets targets and announces whether they have been met in the other policy domains. It highlights the need for ministers and advisers to think carefully about how a reasonable person would interpret a quantitative claim of the sort and to consult the statistical professionals in their department.”
The statistics watchdog also said it had raised concerns with the Home Office after a press release on the backlog was published but without the accompanying data “which prevented (journalists) from being able to scrutinise the data when first reporting it”.
Shadow immigration minister Stephen Kinnock had accused the PM of promoting a “barefaced lie” that was “an insult to the public’s intelligence”.
As the row grew, the claim was denounced as “false” by opposition parties, campaign groups and even Fraser Nelson, the editor of Tory bible The Spectator magazine, who likened the tweet to that of a “snake oil salesman” and urged the PM’s social media team to take the row “as a lesson learned”.