The risque snap popped up on Jones' Fleets — a feature of Twitter where users can post content that disappears after 24 hours — but he reckons he knows nothing about it and was at home with his mother-in-law at the time.
Jones, 50, tweeted his apologies to fans, claiming he'd never heard of Fleets and was going to make sure his account was more secure in future.
After the rude photo briefly appeared on Sunday, he tweeted: "I’ve been hacked sorry everyone! Jeez xxx."
The singer and TV presenter added: "So sorry I dont know what fleets is – Never heard of it!"
An embarrassed Jones wrote: "All back to normal – passwords changed – that was an interesting 20 mins – especially when I’m watching John Wick with the mother in law!!!"
Fleets was introduced by Twitter in 2020 to enable people to share posts for a limited amount of time.
Former chorister Jones first shot to fame as a child in 1985 when he had a chart hit with his cover of Walking In The Air.
He has been a regular presenter on BBC show Songs Of Praise since 2004 and has also hosted various BBC radio programmes as well as on Classic FM.
Jones is still releasing albums as a singer, with his most recent, Blessings, coming out in 2020.
The TV star isn't the only famous person to have suffered a Twitter hack recently. In the US, Graham Ivan Clark was just 17 when he co-ordinated a high-profile hack of celebrity accounts in 2020.
Victims included Kim Kardashian, Kanye West, Elon Musk, Bill Gates and Barack Obama in the Bitcoin scam, which managed to collect $117,000 (£84,200) before it was shut down.
Clark was sentenced to three years and banned from using computers without permission and supervision.