He may have the stage presence and the charisma, but does Robbie Williams have the voice to step into Freddie Mercury's shoes?

Queen's Brian May and Roger Taylor certainly thought so - at least, at one point.

Williams has revealed that the rock legends once asked him to front Queen, after they were impressed by his version of 'We Are the Champions' (from the soundtrack of 2001 film 'A Knight's Tale'.)

However, he said that he turned down the opportunity because of his low self-esteem.

Speaking on Sirius XM, he said: "Even though I’m very confident here on the microphone, I have very low self-esteem. And I just thought I’d save them the audacity of me even trying to step on a stage and be the same echelon as Freddie Mercury.

"He, to me, is angelic. He’s godlike. It was just too scary."

He added that the financial implications of being in a band also put him off. "I was doing stadiums myself at the time," he said. "I didn’t want to have to split it three ways, but that’s another story."

Queen eventually enlisted Bad Company's Paul Rodgers on vocals from 2004 - 2009, and Adam Lambert has fronted the band since 2011. Williams has approved of Lambert's post, too. "Adam Lambert – if he wasn’t such a lovely person, which he is – I would just be terrified of him because of his pure talent," he said. "His voice is absolutely incredible. ‘And he’s an incredible performer, and a lovely person to boot. I’m really pleased when I meet people that I’m just overawed by their talent – he gives me a talent hard-on – and they’re nice."

Williams' most recent album was last year's 'The Christmas Present', while Lambert's new album 'Velvet' is out later this month.