Britney Spears claims the NSYNC star was unfaithful with 'another celebrity' in her memoir. Photo / Getty Images

Rumours that Justin Timberlake cheated on Britney Spears with Nicole Appleton have started to recirculate after the Toxic singer alleged that the NSYNC star was unfaithful with “another celebrity” during their time together.

Spears, now 41, dated Timberlake, 42, between 1999 and 2002.

The pop icon made the shock claims about her former beau in her new memoir The Woman In Me,which is set to hit shelves on October 24. However, she refuses to name the woman because “they have a family and she doesn’t want to embarrass them”, reports the Daily Mail.

Timberlake, who Spears claims got her pregnant and encouraged her to have an abortion in late 2000, was famously spotted with the All Saints star, now 48, as they were heading back to his London hotel after a night on the town in 2000.

The pictures - which have now resurfaced on social media - captured Timberlake, then 19, and Appleton, then 25, concealing their faces in the back of a taxi as they tried to lose the paparazzi.

The two were also snapped walking from The Mayfair Club to St Martins Lane hotel where the SexyBack singer was staying. However, there is no proof that Timberlake was unfaithful while he was with Spears and it is not clear whether Appleton was the celebrity Spears was talking about in her memoir.

The article, with the headline “Nic and guy act so shy”, revealed that Timberlake was still “dating American teen temptress Britney Spears” at the time the pictures were taken.

DailyMail.com has contacted representatives for Timberlake and Appleton for comment.

Back then, Timberlake had been dating the Gimme More songstress for a year and was at the peak of his fame with his boy band NSYNC, while Appleton was enjoying huge success with All Saints - who nabbed a spot on the top 10 US hits list in 1997 with Never Ever.

Appleton and Timberlake never commented publicly on the incident.

Last year, Spears’ former make-up artist Julianne Kaye told The Mirror thatthe singer was jealous of Timberlake’s night out with Appleton.

She said: “I knew they had some issues. She had her questions about who he was with because stuff would be out in the press. They were very famous. So he’d be out with some girl from All Saints and she’d get very jealous, you know what I’m saying?”

Appleton went on to tie the knot with Oasis frontman Liam Gallagher and the pair welcomed a son, Gene, together prior to splitting up in 2014. Appleton filed for divorce from the rocker after it came to light that he had fathered another child in secret.

She then married Stephen Haines in 2021 and they share a daughter Skipper together.

Spears also revealed in her memoir that she had an abortion with the Cry Me A River singer when she was only 19.

The Sometimes singer said she made the “agonizing” decision to terminate the pregnancy, after conceiving at the end of 2000.

In an excerpt obtained by People, she says: “It was a surprise, but for me, it wasn’t a tragedy. I loved Justin so much. I always expected us to have a family together one day. This would just be much earlier than I’d anticipated.

“He said we weren’t ready to have a baby in our lives, that we were way too young. I’m sure people will hate me for this, but I agreed not to have the baby.

“I don’t know if that was the right decision. If it had been left up to me alone, I never would have done it. And yet Justin was so sure that he didn’t want to be a father.”