Timmy Matley, the lead singer of The Overtones, has died aged 36, the band have confirmed.
The singer, from Cork, was diagnosed with stage three malignant melanoma - a form of skin cancer - in 2016.
Matley's agent said the singer "died suddenly" on Monday - the cause of death has not yet been confirmed.
The group posted on Twitter: "It is with great sadness that we have to announce that our dear friend and brother Timmy has passed away.
"We know this news will be as heartbreaking for you all as it is for us."
It is with the greatest sadness that we have to announce that our dear friend and brother Timmy has passed away. We know this news will be as heartbreaking for you all as it is for us. We appreciate your love and support at this difficult time. Mike, Darren, Mark & Lachie x— The Overtones (@the_overtones) April 11, 2018
In a statement, the singer's agent told the BBC: "Singer Timmy Matley died suddenly in London on the 9 April 2018.
"The Overtones singer, from Cork, Ireland, was 36 years old and lived in London. No further details are currently available.
"Family and friends are devastated at the news and have requested privacy at this very difficult time."
Matley announced in December that he was planning a charity skydive to raise money for The Royal Marsden Cancer Charity.
He described the cause as "very close to my heart", and had raised over £5,000 for the skydive, which was due to take place in May.
Phillip Schofield and Scarlett Moffatt have been among those to pay tribute to the singer.
I’m so terribly sorry to hear this and sending lots of love to you all and particularly Timmy’s family and his many friends 😢— Phillip Schofield (@Schofe) April 11, 2018
Such sad news 😪 sending all my love to you all, friends and family xx— Scarlett Moffatt (@ScarlettMoffatt) April 11, 2018
Matley, along with bandmates Lachie Chapman, Mike Crawshaw, Mark Franks and Darren Everest, specialise in doo-wop performances and released five albums, four of which charted in the UK top 10.
Their album Good Ol' Fashioned Love peaked at number four in 2011.
The band first auditioned as a four piece in 2009 for the X Factor, but failed to make it to the live finals.
They became painters and decorators, so they could practise while they were working and were discovered by a talent scout in 2010 during a tea break as they worked at an office near London's Oxford Street.