Walking out of the camera shot with her phone in her hand, she said: "I'm literally going to have to walk off set."
Walker told viewers: "She's walking off, she's embarrassed", before the programme cut to a live shot in Glasgow.
BBC Breakfast presenters
BBC Breakfast presenters
BBC Breakfast presenters Mike Bushell, Louise Minchin, Dan Walker, Naga Munchetty, Carol Kirkwood and Sally Nugent attending the National Television Awards 2017 held at the O2, London. Photo credit should read: Doug Peters/EMPICS Entertainment
BBC handout photo dated 17/1/2008 of BBCBreakfast presenter Bill Turnbull (right), who is leaving the show after 15 years, with other presenters past and present during celebrations to mark the programme's 25th anniversary, including (left to right) Angela Rippon, Francis Wilson, Chris Hollins, Glyn Christian, Selena Scott, Sue Cook, Sian Williams and Mike Smith.
Naga Munchetty attending the BAFTA Craft Awards at the Brewery in London.
BBC Breakfast presenter Naga Munchetty
BBC Breakfast's Mike Bushell during the Mens BBC Breakfast v U23 60m final during the Muller Indoor Grand Prix at Arena Birmingham.
Presenter Mike Bushell during the British Swimming Awards 2018 at the Point, Lancashire County Cricket Club, Manchester
Mike Bushell attends ITV Palooza!, Royal Festival Hall, Southbank, London. Tuesday October 16th, 2018.
BBC Breakfast presenter Louise Minchin
File photo dated 26/9/2014 of former BBC Breakfast presenter Sian Williams who has become the new face of Channel 5's flagship evening news programme, 5 News at 5.
BBC Breakfast presenters (left to right) Sally Nugent, Bill Turnbull and Louise Minchin attend the TRIC Awards at Grosvenor House, Park Lane, London.
BBC Breakfast Weather Presenter Carol Kirkwood, smiles as she arrives at West Newton Village Hall, in Norfolk where she is the guest speaker at the Sandringham Women's Institute, attended by the Queen Elizabeth II.
BBC Breakfast's sports presenter Chris Hollins during the BMW PGA Pro-Am at Wentworth Golf Club, Surrey.
Undated BBC handout photo of BBC Breakfast presenters past and present celebrating the programme's 25th Anniversary, including (Left to Right) Francis Wilson, Mike Smith and Sue Cook.
BBC Breakfast presenter Natasha Kaplinsky arrives for the UK Gala Premiere of Being Julia at the Apollo West End in central London. The film, based on W. Somerset Maugham's 'Theatre' and directed by Istvan Szabo is hotly tipped for the Academy Awards.
Sally Nugent, Dan Walker and Steph McGovern attending the TRIC Awards 2019 50th Birthday Celebration held at the Grosvenor House Hotel, London.
Steph McGovern (left), Dan Walker and Louise Minchin attending the 2018 TRIC Awards at the Grosvenor House Hotel in London. Photo credit should read: Doug Peters/EMPICS Entertainment
Dan Walker during the Pro-Am at Wentworth Golf Club, Surrey.
Louise Minchin, Dan Walker and Sally Nugent attending the 2017 TRIC Awards, held at the Grosvenor House Hotel, London.
Picture date Tuesday March 14, 2017. Picture credit should read Doug Peters/ EMPICS Entertainment
BBC Breakfast presenter Charlie Stayt (centre), Louis Minchin (left) and Naga Munchetty (right)
(left to right) Jim Kriegshauser, nephew of John Kriegshauser, Megan Leo, cousin of airmen George Williams (who both died in the Mi Amigo crash), Tony Foulds, with BBC presenters Charlie Stayt and Steph McGovern as they watch from Endcliffe Park in Sheffield, as warplanes from Britain and the United States stage a flypast tribute to ten US airmen 75 years after the crash that killed them.
Naga Munchetty at The TRIC Awards (Television and Radio Industries Club Awards) at Grosvenor House, Park Lane (Photo by Keith Mayhew / SOPA Images/Sipa USA)
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He could also be heard saying: "That's Louise's new podcast, The TriPod."
Minchin, who is a keen triathlete, launched the new show on BBC Radio Manchester on Monday night.
She later rejoined Walker on set and told viewers: "I'm really properly embarrassed."
The pair burst into giggles as Walker said: "It's still going, have we managed to turn it off?"
She covered her mouth with her hand as she said: "How have I done that? I genuinely don't know what I did. I apologise profusely."
After a short segment about the Clyde Bridge in Glasgow, Walker said: "Back in the studio, Louise is still a little bit embarrassed by the fact she sat on her phone and played her own programme."
Minchin later tweeted: "Oh my gosh! My phone is out of control. #apologies I think a banning order might be in order."
When one viewer asked her if it was a "shameless plug", she joked: "I couldn't have timed it better if I had actually tried to."