The 'Let Me Entertain You' star left the band for a second time in April 2014, only to be followed by Jason in September of the same year.
The 44-year-old singer was asked by Phillip Schofield and Holly Willoughby on UK TV show 'This Morning' on Tuesday (19.06.18) to confirm rumours the band are plotting a full reunion - with him and Jason joining Gary Barlow, Mark Owen and Howard Donald to mark their 30th anniversary in 2020.
He said: ''I can genuinely say I don't know. I'm up for it. But I don't know what their calendar says, what my calendar says. I don't know what their manager says.
''We'd all love to do it. I'd love to get Jason back involved, realistically I don't think so.
''If we could get Jay back it would be perfect. But we shall see, watch this space.''
In March, Gary admitted there was ''no chance'' of Robbie rejoining the band.
The 47-year-old singer was adamant that the part-time member is highly unlikely to want to perform or work on new music with his bandmates after Robbie said he'd only return if Jason did too.
Gary said: ''I wouldn't put money on that. Don't waste your money. I would say there's no chance.''
However, his bandmate Mark wouldn't rule it out, he said: ''I wouldn't say there's no chance, but I've always said that.''
The five of them last performed together in 2011 on the 'Progress Live' tour for the first time in 15 years, but Gary said he's happy continuing as a three-piece.
He said: ''We feel like we did that whole five of us in 2011, so we're alright for a bit. We're not sitting around waiting for people to come back.''
In the Hall By The Sea at Dreamland, Reef brought their Revelation tour to life as they delivered one of the best live sets I've had the privilege to...
'Worst Nites' is the music video directorial debut of 'The Hunger Games' star Josh Hutcherson with Foster the People's frontman Mark Foster.
Matty Healy of The 1975 plays an acoustic rendition of the song '102' which features as a bonus track on the Japanese edition of their third album.
Having dropped her number one second album 'Always In Between' in October 2018, Jess Glynne unveils the video for her catchy new single 'Thursday'.
It's been four years since he dropped his number one self-titled debut album, and now Hozier's back with a new single entitled 'Movement'.
Andy Burrows has teamed up with author Matt Haig on an album version of the latter's memoirs, 'Reasons To Stay Alive', which is set to be released on...
As the nights draw in and the temperature drops, Crooked Man treats us to a fabulous slice of sun-soaked House, Disco and Electro.
Sydney trio Mansionair have dropped the video for their new single 'Falling' as they gear up for their first North American headline tour.