The comedian and presenter, 57, who is best known for hosting Channel 4 gameshow Taskmaster, appeared on the daytime talkshow to discuss his recent tour.
Greg Davies was left shaking his head and gasping 'this is not how I thought this would go' after joining Lorraine Kelly on her self-titled ITV show on Tuesday.
The comedian and presenter, 57, who is best known for hosting Channel 4 gameshow Taskmaster, appeared on the daytime talk show to discuss his recent tour.
However, Greg was left in shock when talk turned to his recent television appearances, as Lorraine, 65, made a very rude jibe about women's knickers.
Earlier in the show, Lorraine had gushed over 'crush' Greg, admitting he had a 'lot to be confident about', telling him: 'We think you're very handsome.'
And later talk turned to his recent tour, Full Fat Legend, which has been extended with more dates next March thanks to its popularity.
Discussing how Greg took to the Graham Norton show earlier this year to speak about the tour, talk soon turned to a shock admission that the comedian made on the BBC series: that he had once accidentally worn his mother's knickers.
Greg Davies was left shaking his head and gasping 'this is not how I though this would go' after joining Lorraine Kelly on ITV
Greg was left in shock when talk turned to his recent television appearances, as Lorraine, 65, made a very rude jibe about women's knickers
Greg tried to explain of the mistake: 'I went home, and my mum did my washing for me, and some of her knickers got in there, and I put them on.'
It was then that Lorraine told him: 'Your trousers are so big and long that you could get loads of pairs of knickers in there, so it isn't your fault.'
Shaking his head, Greg replied: 'God, this interview hasn't gone the way I thought it would go...'
The duo were left laughing at one another, with Lorraine sitting back and covering her mouth realising what she'd just said to Greg, who awkwardly shook his head.
'We're not going to end on "your trousers are so big you could get loads of knickers in there, are we?"' Greg asked her, as Lorraine struggled to contain herself and wiped her eyes.
Signing off the. interview, Greg joked once more: 'Thank goodness I've got jeans big enough to fit a thousand pairs of knickers inside them.'
Greg revealed that he had once accidentally worn his mother's knickers, prompting Lorraine to respond with the shock comment about his 'big, long jeans'
It comes after Greg revealed he credits a midlife meltdown in a flotation tank for his decision to swap a teaching career for stand-up comedy.
'I couldn't stop crying for the whole day and I couldn't understand why,' he said.
'The day after, I couldn't stop crying. Day three, I thought, okay I've gone mad.'
A few days later, he met the owner of a flotation tank centre at a barbecue who told him that such reactions were common.
'You get to such a stage of relaxation that lots of things you've suppressed get released into your system,' he said. 'It was a real turning point.'
That night, after 13 years as an increasingly unhappy English and drama teacher, he applied to do a course in stand-up comedy.
He blames his father, an academic, for pushing him towards teaching.
'I thought it would just be a stepping stone – I hadn't banked on my own cowardice,' he told Desert Island Discs.
Greg returned to screens last month alongside co-star Alex Horne as their popular gameshow returned for its 20th series on Channel 4.
Inside No. 9's Reece Shearsmith and Unforgotten's Sanjeev Bhaskar were among the impressive celebrity-packed line-up for the series.
Stand-up comics Ania Magliano, Maisie Adam and Phil Ellis will also feature.
Lorraine airs weekdays from 9am on ITV1 and is available to stream on ITVX.