In an exclusive chat with ITV News Political Correspondent Paul Brand, Ms Rayner and her mum Lynn Bowen appeared on camera for the first time in a revealing interview.
Ms Rayner also took part in Paul's Acting Prime Minister podcast - which you can watch above or listen to on any platform - and spoke about a wide range of topics.
While she was growing up, her mother was in a battle with severe depression, suicidal thoughts and caught in a revolving door of poverty, struggling to feed her kids.
Rather than being a daughter, Ashton-under-Lyne MP Ms Rayner was forced to act as her mother's permanent carer.
"I was in a very dark place, she used to bath me, look after me, feed me," Ms Bowen said of her daughter.
"If it wasn’t for her I don’t think I’d be here today," she added.
At one stage, fearing for her mother's safety, Ms Rayner was forced to have her mother admitted to a mental health ward over her suicidal thoughts.
Ms Bowen said: "I was really depressed and suicidal, [Angela] had me sectioned once...because I cut my wrists, took the tablets, [she] had to get the police and the ambulance."
She says Angela "went through everything" as a youngster, and told how her behaviour was "brilliant".
"All what she’s been through and everything, she’s come through it all and I’ve got to look at it that she’s had to go through this, down this road...she’s gone through everything, got me in a stable way or else I wouldn’t be sitting here today, and look at her, look where she is," she said.
Taken aback at hearing the praise, Ms Rayner said "my mum doesn’t say stuff like that often so it’s nice.
"It’s nice that my mum is proud of me, because I’m proud of her."
It may seem a harrowing experience, but for Ms Rayner - who had a child herself at the age of 16 - looking after her mother was all she ever knew.
"I remember being scared, remember staying at the bottom of my mum’s bed once, thinking is my mum going to do something, and not wanting to go to sleep because I didn’t want to go to sleep and think my mum wouldn’t be there in the morning, and that was quite traumatic," she told Paul.
Ms Bowen admits her daughter "had it rough" and sometimes gets "upset with the way that Angie has had to grow up pretty fast".
"I always picture her as the mum when I was having that really dark time because I was acting like a baby, because that’s all I could do," she added.
Ms Rayner remembers the tough times, looking back to a period when her mother was on benefits with no food in the cupboards.
"We grew up in poverty, you were on giros weren’t you, you were on benefits," she said to her mum during the interview.
"We was waiting for food to come into the cupboards and stuff," she added.
But Ms Rayner's mum believes the tough childhood made her a "lot stronger".
And Ms Rayner agrees.
"I was so frightened of what I saw my mum go through that I never wanted to experience that.
"So therefore I’ve always been quite resilient as an individual because of that, because I’ve not wanted to end up in that place because I’ve seen how painful it was," she said.
Ms Rayner, who wants to succeed Tom Watson as the next deputy leader of Labour, also criticised the party's current leader in the interview.
She said Jeremy Corbyn, who is due to be replaced by a new leader on April 4, "didn't command respect" within the party.
Ms Rayner, who is the favourite to become Labour's deputy leader, told ITV News Political Correspondent Paul Brand that she'd be tougher than Mr Corbyn in several ways.
"I'm more bombastic, more focused and more sharp, and I would expect more discipline in a way that Jeremy didn't," she said.
"He didn't command respect, and he therefore wasn't able to command that collectivism in the Labour Party."
Touting her leadership credentials, she said she has "respect" and "support" right across the Labour Party and claimed she is able to "resonate with people in the country in a way that Jeremy doesn't."
She suggested - unlike leadership candidate Rebecca Long-Bailey - that current leader Mr Corbyn should not be admitted to the shadow cabinet once he's been replaced.
When asked about Mr Corbyn's potential role on the frontbench, she said: "I think now the opportunity should be for the next generation to come forward."
She also criticised the party's Brexit position.
"Our Brexit position was awful, people did not accept where we were at on that," she told Paul Brand, "and our manifesto was too much, people just didn't think it was credible."
And she claimed she would be more "pragmatic" than Mr Corbyn in terms of security.
She said: "I think I'm stronger on security, I've always felt quite strong about that."
While her childhood experience certainly readied Ms Rayner for motherhood and even public life as an MP, her mum thinks she could one day lead the country.
Asked what she makes of Angela's bid to be Labour leader, Ms Bowen laughed and said: "Watch this space, my daughter will be running this country in a few years time."
"She can do it - she could do it now if she wanted...watch this space. No one else can do the job but my daughter! I am so proud of her, I really am," she said.
"She’ll be the prime minister soon, watch out Boris you won’t be there for long."
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