The Prime Minister has credited “relentless action” after the Government announced it met a target to clear a backlog of asylum claims.

The Home Office said on Monday that Rishi Sunak’s “commitment of clearing the legacy asylum backlog has been delivered” and it had processed more than 112,000 asylum cases overall in 2023.

Officials also made the “highest annual number of substantive decisions in a year since 2002”, it said.

Mr Sunak told the Daily Express: “The progress is the result of relentless action to tackle illegal migration over the past year.

“When I set out my blueprint to stop the boats, abolishing the legacy backlog was a key part of it.”

Mr Sunak previously pledged to remove the older asylum applications by the end of 2023, tasking the Home Office with tackling the number of so-called “legacy” claims.

But Labour accused the Government of making false claims about meeting the target, with figures suggesting the department had fallen short of the number initially set to reach.

The Home Office said all cases in the legacy backlog have now been reviewed, with 86,800 decisions made, but “4,500 complex cases have been highlighted that require additional checks or investigation for a final decision to be made”.

Such cases typically involve “asylum seekers presenting as children – where age verification is taking place; those with serious medical issues; or those with suspected past convictions, where checks may reveal criminality that would bar asylum”, the department added.

Ahead of official figures being published on Tuesday morning, it is understood the Home Office has processed around 25,200 newer asylum claims, in addition to 86,800 decisions in legacy cases, taking the provisional number of total decisions made overall in the year to 112,000.

Officials say as many decisions as possible were made in the legacy backlog, and outstanding cases were because the department would not compromise on security and needed to make sure additional checks were carried out. They believe efforts to also clear a chunk of newer cases at the same time points towards the commitment to tackling the overall asylum backlog.

In one four-week period from November 20 to December 17, there were 20,481 initial asylum decisions made – more than the number of asylum decisions made in the entirety of 2021, the Home Office said.

The grant rate for final asylum decisions on fully completed cases in 2023 stood at 67%, lower than in 2022 and 2021 (76% and 72%).

Setting out a five-point plan in a bid to grip the migrant crisis in the Commons in December 2022, Mr Sunak said “unless we act now, and decisively, this will only get worse”.

Among a raft of new measures unveiled to curb Channel crossings, he told MPs “we expect to abolish the backlog of initial asylum decisions by the end of next year” after hiring more caseworkers and overhauling the system for processing applications.

But his vow was almost immediately called into question by Labour amid confusion over the scale of his ambition.

Within hours of the announcement, Downing Street appeared to downgrade the target to say only a portion of outstanding applications would be cleared, insisting the Prime Minister had only committed to addressing the backlog of 92,601 initial asylum claims made before June 2022, when the Nationality and Borders Act came into force.

In February last year, the Home Office said thousands of asylum seekers would be sent questionnaires which could be used to decide their claims, as part of efforts to cut the soaring backlog of cases and speed up the processing of applications.

About 12,000 people from Afghanistan, Syria, Eritrea, Libya and Yemen, who had applied for asylum in the UK and were waiting for a decision, were understood to be eligible under the policy which would see them being asked to fill out the form instead of being automatically interviewed.

Whitehall’s spending watchdog said in June that efforts to clear the asylum backlog needed to significantly increase to meet Mr Sunak’s target and questioned whether the plans were sustainable.

The National Audit Office also estimated £3.6 billion was spent on asylum support in 2022-23, almost double the amount in the previous year.

MPs later asked senior Home Office officials how the target was being met, as figures showed 17,316 asylum applications were withdrawn in the year to September 2023 – a sharp rise which was more than four times the number for the previous year when there were 4,260. They also expressed surprise when the officials suggested the department did not know the whereabouts of these asylum seekers.

The Commons Home Affairs Committee heard in November that claims were withdrawn when asylum seekers did not turn up for interviews or complete questionnaires and were “not engaging with the system that leads to a decision”.

Other reasons included when someone had already left the UK before their claim was considered, or if they chose to pursue another application for permission to stay in the country, according to the department.

The Home Office said more caseworkers had been tasked with processing applications, which was “tripling productivity to ensure more illegal migrants are returned to their country of origin, quicker”.

But last month the department’s top civil servant, permanent secretary Sir Matthew Rycroft, revealed in a letter to MPs that since 2020, just 1,182 migrants who had crossed the Channel had been returned to their home country out of a total of more than 111,800 who arrived in that time period.

The majority of those were Albanian – a country with which the UK has a returns agreement – and there were only 420 who were sent back to other countries.

Asked if that was an “acceptable figure” by the Home Affairs Committee, illegal migration minister Michael Tomlinson replied: “As far as I’m concerned the numbers need to be significantly higher than they are.”

Mr Sunak said he was “determined to end the burden of illegal migration on the British people”, adding: “By clearing the legacy asylum backlog, deciding more than 112,000 cases, we are saving the taxpayer millions of pounds in expensive hotel costs, reducing strain on public services and ensuring the most vulnerable receive the right support.

“But we cannot be complacent, which is why I am focused on delivering on my commitment to stop the boats and get flights off the ground to Rwanda.”

Labour’s shadow immigration minister Stephen Kinnock said no “slicing or renaming the figures can disguise” that the asylum backlog had “rocketed under the Tories”.