Labour's former chief whip queried Jeremy Corbyn's decision to promote an MP, following allegations of sexual harassment, the BBC has learned.
Dame Rosie Winterton rang the Labour leader's office to ask why Kelvin Hopkins had been appointed to the shadow cabinet in July 2016.
She reminded them that Mr Hopkins had been reprimanded for harassing a young activist, a Labour source said.
The Labour Party has not officially commented on the claim.
A party spokesman said an investigation is ongoing into the allegations about Mr Hopkins's conduct and it takes such complaints "extremely seriously".
Mr Hopkins, 76, was promoted to Jeremy Corbyn's frontbench team in July 2016 but asked to return to the backbenches four months later.
He has not commented on the allegations about his past conduct but has been suspended while the party investigates them.
Labour activist Ava Etemadzadeh, 27, earlier told the BBC she had been left feeling "very powerless and isolated" after Mr Hopkins was promoted - the year after she complained about his behaviour.
Ms Etemadzadeh claims the Luton North MP made inappropriate physical contact while hugging her, after she had invited him to speak at a university event in 2014, which "made me feel extremely uncomfortable".
"The second incident was in Parliament when I went to have a conversation and he told me that 'let's not talk about politics, do you have a boyfriend?'," she told BBC News.
"And he also said that if nobody was in his office he would've taken me there. I was absolutely shocked and I wasn't really expecting that."
After refusing to respond to his phone calls, she claimed he sent her a message "saying that I'm an attractive, lovely young woman and a man would be lucky to have me as a lover and if he was young ... but he's not".
Some months later she raised concerns about Mr Hopkins' conduct with another Labour MP and her complaint was passed to the party's then chief whip Dame Rosie Winterton, who responded to it.
But Ms Etemadzadeh said she was told she would have to waive her anonymity for action to be taken and the prospect of this "scared" her.
It is understood Mr Hopkins was verbally reprimanded about his alleged behaviour.
But he went on to be promoted, albeit briefly, to Labour's front bench in June 2016 - shortly after leader Jeremy Corbyn faced mass resignations following the EU referendum.
Ms Etemadzadeh told the BBC she believed that the Labour leader's office had been contacted about the complaint "and it was ignored".
"I'm very disillusioned because just a few months later I realised that Jeremy Corbyn promoted Kelvin Hopkins to the shadow cabinet, despite the fact that the leader's office was aware of this and they refused to act and that made me feel very powerless and isolated and alone."
Labour MP Jess Phillips told the BBC earlier: "I am a bit concerned about the fact that Kelvin was then promoted afterwards, that does seem wrong to me... I think that people just didn't take it as seriously as it needed to be taken."
Who is Kelvin Hopkins?
- Labour MP for Luton North since 1997
- Spent most of 20-year political career on backbenches
- Briefly promoted to front bench from July to October 2016
- Long history of involvement with trade union movement
- One of 36 MPs to nominate Jeremy Corbyn for his 2015 leadership bid
- One of the few Labour MPs to campaign for Leave in the EU referendum
- Married to Patricia. The couple have two grown up children
Asked about the story, Shadow Commons leader Valerie Vaz told BBC Radio 4's World at One: "The issue has come to light and and the matter is being thoroughly investigated by the party."
Last week Mr Corbyn said he would encourage any woman who had been abused or harassed by MPs to speak out, adding that the party's National Executive Committee (NEC) had adopted new "robust" procedures to deal with the issue in July.