Blunderings couriers lost hundreds of passports and key documents despite the number sent out plummeting.
Families desperate for a holiday abroad are seeing their hopes dashed as the service is mired in chaos and backlogs.
Bungling bosses stand accused of failing to predict a surge in passport applications when international travel reopened after the coronavirus pandemic.
The shambles has triggered questions in Parliament and pledges that more staff will be recruited to ease delays.
The Mirror can reveal that even as the number of passports sent out dwindled in 2020 and 2021 when travel curbs were in force, the number lost by delivery courier TNT, which has the exclusive contract, rocketed.
A freedom of information request to the Passport Office showed that in 2018 it issued 6,681,299 passports.
Some 422 passports or “supporting documents” were lost “during delivery by courier” - 0.006%.
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The figures were broadly similar the following year when 6,707,500 were issued and 437 were lost.
But in 2020, when planes were grounded and many countries closed their borders, the number of passports issued plummeted to 3,948,060 - yet the number lost while being dispatched climbed to 519.
Last year, when restrictions on foreign travel still hampered many business trips and holidays, 4,823,620 passports were issued.
But the number lost during delivery by courier spiralled to 1,196 - and that only covers 2021 to July.
Prospect union general secretary Mike Clancy said: “Lack of government investment has already caused passport chaos, with many families facing huge uncertainty about whether they will get away for a break this summer.
“Now we find out that the privatised delivery service is losing passports at a record rate too.
“It’s time for the Government to actually invest in public servants rather than threatening massive, damaging cuts to the civil service.”
Last month, Boris Johnson threatened to “privatise the a***” out of the Passport Office over delays.
But critics pointed out some of the problems lay with TNT, which was awarded a £77million, three-year deal in July 2019. The contract is due to run out this summer.
Shadow Home Secretary Yvette Cooper said: “The passport crisis is a total scandal.
“Families are missing out on hard-earned breaks and losing thousands in cancelled holidays, all because of Home Office ministers’ incompetence.
“Delays in decisions and problems with deliveries are causing a total nightmare for families who have been really looking forward to a first holiday away after Covid.
“Boris Johnson may have threatened to privatise the Passport Office but as the Mirror's data makes clear, it's the private contracts that are causing some of the worst problems.
“Ministers need to get a grip of the TNT contract and sort out the delays before more families lose out.”
Lib Dem home affairs spokesman Alistair Carmichael said: "The sheer number of passports going astray during delivery simply isn't good enough.
“The Home Office is presiding over a sloppy shop.
"It's high time ministers get a grip of this mess and step in to save the summer holidays for people left waiting on passports that'll never arrive."
A spokeswoman for FedEx, which owns TNT, said: “Last year, when Covid-19 restrictions eased, we saw a significant increase in items being delivered through our dedicated HMPO (Passport Office) network.
“This had a regrettable, short term impact on service levels, which were restored after taking a number of operational actions.
“Since December 2021, we have been operating successfully within the service level requirements agreed with HMPO and we continue to stay focused on providing a reliable service for our customers.’’
A Passport Office spokesman said: “Between January 1 and July 31 2021 HM Passport Office sent over 3.3 million items to its customers.
“While regrettable, less than 0.04% of those were reported as having been lost during delivery, and many of those items have been subsequently recovered.
“The safety of our customers’ personal data is of paramount importance and every attempt is made to recover lost or mis-delivered documents.
“Once reported, passports are cancelled on the system immediately in order to mitigate against the risk of misuse and we continue to work with our delivery partner to develop measures to reduce the number of losses overall.”
