Labour leadership hopeful Lisa Nandy became embroiled in a heated row with TV presenter Piers Morgan over the issue of transgender rights.
The Wigan MP demanded the Good Morning Britain host apologise after he repeatedly asked her to say whether she felt it was "unfair" for athletes who now identify as female to compete in women's sport.
Ms Nandy, who has backed pledges from the Labour Campaign for Trans Rights that call for the expulsion of transphobic members from the party, said it was for sporting bodies to establish a commission to discuss the issue.
But Morgan demanded Ms Nandy give a "straight answer" and pressed her again, citing the example of New Zealand weightlifter Laurel Hubbard, a transgender woman who is now targeting selection for the Olympics having previously competed as a male weightlifter.
He also posed a hypothetical question over whether world record-holding sprinter Usain Bolt should be allowed to compete against women if he decided to transition.
Piers Morgan (centre), editor of The Mirror, leaves the High Court in London after supermodel Naomi Campbell won 3,500 damages from the newspaper following a ruling that it acted in breach of confidence in publishing details of her therapy at Narcotics Anonymous.
Mayor of London Boris Johnson (left) with Piers Morgan during a party to celebrate the 180th Anniversary of weekly politics magazine The Spectator, held at the Churchill Hyatt Hotel in central London.
Piers Morgan, former Daily Mirror Editor and Arsenal fan
2019 British Academy Britannia Awards - Arrivals - Beverly Hills, California, U.S., October 25, 2019 - Piers Morgan. REUTERS/Mario Anzuoni
Broadcaster Piers Morgan arrives at the BBC to appear on The Andrew Marr Show in London, Britain, January 28, 2018. REUTERS/Hannah McKay
Britain Golf - British Masters - The Grove, Hertfordshire - 12/10/16
Piers Morgan tees off at the 12th hole during the Pro-Am
Action Images via Reuters / Paul Childs
EDITORIAL USE ONLY.
TV personality Piers Morgan and actor Gerard Butler (R) arrive on the red carpet at the annual White House Correspondents' Association dinner in Washington April 27, 2013. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS ENTERTAINMENT)
Piers Morgan of CNN arrives for a party thrown by Google and the Hollywood Reporter, on the eve of the annual White House Correspondents' Association Dinner, at the W Hotel in Washington, April 27, 2012. REUTERS/Jonathan Ernst (UNITED STATES - Tags: ENTERTAINMENT MEDIA POLITICS)
British talk show host Piers Morgan and former News of the World editor arrives for work at CNN after his British judicial inquiry in Los Angeles, California December 20, 2011. Morgan told a British judicial inquiry on Tuesday that he had never approved phone hacking during his time as a tabloid newspaper editor, and that his published boasts had merely been repeating rumours about journalistic ``dark arts.'' REUTERS/Gus Ruelas (UNITED STATES - Tags: CRIME LAW ENTERTAINMENT MEDIA)
Piers Morgan, host of "Piers Morgan Tonight," poses during the Turner Broadcasting Television Critics Association winter press tour in Pasadena, California January 6, 2011. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT)
Model Naomi Campbell (L) walks down the catwalk with British television personality Piers Morgan during the Fashion For Relief Haiti fashion show and auction in London, February 18, 2010. REUTERS/Suzanne Plunkett (BRITAIN - Tags: FASHION)
Former Daily Mirror editor Piers Morgan takes his seat ahead of the English premier league soccer match between Arsenal and Leicester City at Highbury, London, May 15, 2004. Morgan was sacked after the newspaper conceded that photos they had published of British soldiers abusing an Iraqi were fake. NO ONLINE/INTERNET USAGE WITHOUT FAPL LICENCE. FOR DETAILS SEE WWW.FAPLWEB.COM REUTERS/Mike Finn-Kelcey MFK/DBP/ACM
Editor of Britain's Daily Mirror newspaper Piers Morgan leaves his home in London, May 14, 2004. Morgan, editor of London's Daily Mirror newspaper, was ousted on Friday over publication of pictures of alleged abuse of Iraqi prisoners by British troops that proved to be fake. "The Board of Trinity Mirror has decided that it would be inappropriate for Piers Morgan to continue in his role as Editor of the Daily Mirror and he will therefore be stepping down with immediate effect," the newspaper said in a statement.
Judge Piers Morgan speaks on stage, during the 69th Miss World annual final at the ExCel London.
Lucie Donlan and Piers Morgan at the ITV Palooza at the Royal Festival Hall, South Bank (Photo by Keith Mayhew / SOPA Images/Sipa USA)
Piers Morgan and Susanna Reid arriving for the ITV Palooza held at the Royal Festival Hall, Southbank Centre, London.
World Eleven Assistant Manager Piers Morgan celebrates with the trophy at the end of the Soccer Aid match at Stamford Bridge, London.
The Prince of Wales meets Piers Morgan during a visit to the London Television Centre, Lambeth, to celebrate the 90th anniversary of the Royal Television Society.
Embargoed to 2030 Wednesday March 1 Piers Morgan arrives at the Design Museum in London for the launch of the new Range Rover Velar.
Eamonn Holmes and Piers Morgan (right) attending the ITV Gala at the London Palladium. PRESS ASSOCIATION Photo. Picture date: Thursday November 19, 2015. See PA story SHOWBIZ ITV. Photo credit should read: Ian West/PA Wire
Kevin Pietersen (left) and Piers Morgan take part in the BGC Annual Global Charity Day at Canary Wharf in London.
Celia Walden and Piers Morgan at the Glamour Women of the Year Awards in Berkeley Square, London.
Piers Morgan and Amanda Holden during the National Television Awards 2010, at the 02 Arena, London.
Katy Perry with the award for Aussie Hare Care Newcomer and Piers Morgan, at the Glamour Woman of the Year Awards 2009, at Berkeley Square Gardens, W1
Piers Morgan arrives at the Spectator and GQ 200th Anniversary Party ÐÊPolitics Meets Style, at Sir Rocco Forte's Brown's Hotel in central London.
Piers Morgan and Konnie Huq launch the UK's top 100 'green-agers' who will take part in the npower Climate Cops programme, London.
Fearne Cotton and Piers Morgan during a photocall to launch npower's search to find 'green-agers' across the UK to take part in it's Climate Cops programme, in Regents Park, central London.
Piers Morgan (L) and Andrew Neil attending the Grand Final of Miss Great Britain 2007, held at Grosvenor House hotel in central London.
Discover More Like This
BACK TO SLIDE
Ms Nandy accused Morgan of being "irresponsible" and pitting women's rights against trans rights.
She said: "It's for sport to have a proper commission to sit down and work out where those boundaries are.
"I will not allow this to become a zero sum battle between two groups of people.
"I will tell you why, because you are doing what too many people have done in this debate – you have created more heat and less light.
"It's just simply nonsense, it's a straw man."
She added: "I'm giving you a straight answer, I'm saying you are setting up a straw man in order to to pit one group against another.
"It has a real world impact and you need to stop it.
"You are attacking some of the most marginalised people in the country."
Morgan insisted he was "not attacking transgender rights" and again demanded Nandy say whether she felt it was fair for trans athletes with "superior strength and power" to enter in women's competitions.
As the GMB jingle played the show into an advert break, the pair continued to talk over each other and Nandy said: "I want you to apologise."
The heated debate started when Morgan had asked Ms Nandy if she agreed with her Labour colleague Dawn Butler, who he said had told the show recently that children are born without sex.
Ms Nandy replied that when babies are born, they are "designated" a biological sex, which is "determined by their physical attributes".
"It's not for me to tell people who they are," she said.
Morgan asked her about a BBC Teach video that suggests there are more than 100 gender identities, to which Ms Nandy replied: "You could do with watching one."
She added: "People choose their own gender, they choose how to define themselves, I believe."
When Morgan repeated that he could choose to identify as a "two-spirit penguin", a claim which drew scores of complaints last September, Ms Nandy joked it would be a "dramatic improvement".
The issue of trans rights has become the subject of debate in the Labour leadership contest and even prompted former Labour prime minister Tony Blair to warn the party should not fight the "culture war" on trans rights.