First reported by the BBC, the news was confirmed by the U.K. Health Minister Matt Hancock later on Thursday.
"We've agreed to join forces with Google and Apple, to bring the best bits of both systems together," said Hancock at the daily Downing Street briefing in London.
The reason for the U-turn relates to a technical barrier, Hancock admitted.
"We found that our app works well on Android devices, but Apple software prevents iPhones being used effectively for contact-tracing unless you're using Apple's own technology," he said.
The U.K.'s NHSX, the innovation arm of the National Health Service, initially set out to build its own app without the help of the U.S. tech giants.
However, soon after the U.K. began developing its app, Google and Apple announced their own product. Since the announcement, the U.K. has been working on two versions of the app, Hancock said.
"As it stands, our app won't work because Apple won't change their system," Hancock said. "But it can measure distance, and their app can't measure distance well enough to a standard that we are satisfied with."
The U.K. now wants to combine the NHSX algorithm, and the work that it's done on distance calculations with Apple and Google's work, to deliver a new solution, according to Hancock.
Contact-tracing apps log when two people have been in close proximity to one another for an extended period of time. If someone contracts the virus then an alert will be sent to people they've been in close proximity to.
Apple and Google's platform is designed to offer citizens more privacy but it doesn't give epidemiologists access to as much data.
Germany, Italy and Denmark have also switched from a so-called "centralized" approach that sees data processed on a state-controlled server to Apple and Google's "dencentralized" approach, where data is processed on the handset itself, thereby limiting privacy intrusions.
The U.K. government said that the NHSX's contact-tracing app was a key part of lifting the country's lockdown and that it would help reduce the chance of a second wave of the coronavirus.
Development on the U.K. app started in March. Within weeks, however, Apple and Google announced that they were teaming up to develop technology that would help smartphones to make Bluetooth "handshakes" with other smartphones in the background, meaning the contact-tracing app didn't have to be open at all times.
There was one caveat: They said they would only allow these background handshakes to occur on "decentralized" apps.
The U.K. started piloting a centralized contact-tracing app on the Isle of Wight, home to 142,000 of the U.K.'s 66 million population, on May 7.
It was aiming to have it up and running nationwide by mid-May, but that date has now slipped to winter.
"We are seeking to get something going for the winter, but it isn't the priority for us at the moment," said Lord James Bethell, the minister for innovation at the Department of Health and Social Care, in response to a question about the app on Wednesday.
Within days of the pilot going live, it emerged that the U.K. was contemplating a move to Apple and Google's framework and it has been trialing both versions side-by-side for several weeks now.
Former Apple executive Simon Thompson has been put in control of the heavily-delayed project, while NHSX CEO Matthew Gould is stepping aside, according to a separate BBC report on Wednesday.