The Labour leader made the pledge during a phone call to Dame Esther Rantzen, in a major victory for the Daily Express's Give Us Our Last Right campaign.
Childline founder Dame Esther, 83, has reinvigorated the battle for greater choice at the end of life since revealing her stage four lung cancer diagnosis and decision to register with Dignitas.
Sir Keir told her: "I'm personally in favour of changing the law. I think we need to make time.
"We will make the commitment. Esther, I can give you that commitment right now."
Speaking to the Express afterward, Dame Esther said Sir Keir had raised concerns about assisted dying becoming a "political football", with other parties feeling obliged to oppose it if Labour makes a manifesto commitment on holding a debate.
But his personal commitment was "crystal clear", she said.
She added: "He told me that when he was director of public prosecutions, every single case where assisted dying was suspected was referred to him to decide if the loved ones left behind should be prosecuted. So he has heard the stories of terrible suffering imposed by the current law.
"And he added compassion to the criteria. But he admitted that was not enough to protect loving, compassionate families from a police investigation, which is the danger if I have to go to Dignitas and want my wonderful family to come with me to say goodbye."
Dame Esther implored MPs who had not personally experienced the painful death of a loved one to listen to the wealth of heartbreaking stories and evidence from around the world.
She added: "Obviously there must be careful precautions in any new law to protect the vulnerable. Sir Keir is fully committed to that.
Esta historia es de la edición March 13, 2024 de Daily Express.
Comience su prueba gratuita de Magzter GOLD de 7 días para acceder a miles de historias premium seleccionadas y a más de 9,000 revistas y periódicos.
Ya eres suscriptor ? Conectar
Esta historia es de la edición March 13, 2024 de Daily Express.
Comience su prueba gratuita de Magzter GOLD de 7 días para acceder a miles de historias premium seleccionadas y a más de 9,000 revistas y periódicos.
Ya eres suscriptor? Conectar
'Sir Jim has only been negative for United'
SCHOLES SAYS RATCLIFFE HAS DONE NOTHING GOOD
TIME TO TEST METTLE
Beaumont backs chances of upsetting Aussie 'aura'
Care so lucky in love with Quins
SCRUM-HALF PLANS FOR 20-YEAR ANNIVERSARY
DREAM TEAM START WORK DOWN UNDER
NOVAK DJOKOVIC has trained with new coach Andy Murray in public for the first time, ahead of the Australian Open.
60% dismiss signs of dementia as old age
SIX in 10 adults put early signs of dementia down to old age rather than the condition, a survey reveals.
Early coffee helps fight off fatal heart attacks
COFFEE in the morning reduces the risk of a deadly heart attack or stroke more than downing it all day, suggests research.
Raging Norrie so sorry as his racket hits spectator
FRUSTRATED tennis ace Cameron Norrie was lucky to avoid being disqualified after striking a woman with his racket which he had hurled in fury during a match.
Far-Right unifier Le Pen dead at 96
FAR-Right French politician, convicted holocaust denier and antisemite Jean-Marie Le Pen has died at 96.
Veteran's plea to reunite heroes for 80th anniversary
HERO Geoff Roberts has issued an SOS in the hope of reuniting his chums at the scene of their finest hour.
Abuse was played down by politically correct cowards
'Young white women were seen as fair game for predation’