Ms Rayner said she had “reflected” on the tone of political debate in the wake of the murder of Conservative MP Sir David Amess and would no longer use such language.
The apology came as two men were arrested and another was charged and pleaded guilty in relation to allegedly threatening and abusive phone calls, letters and email messages directed at Rayner in recent weeks.
Ms Rayner, who has been away from parliament on compassionate leave after a bereavement, said that threats against her life have had a “devastating” impact on her.
She said that her staff were bearing much of the brunt of abuse and should not be in a position where
they are having regularly to liaise with police about death threats and their personal safety.
Ms Rayner came under fire after reports of a meeting on the fringe of Labour’s Brighton conference last month, in which she was quoted as saying: “We cannot get any worse than a bunch of scum, homophobic, racist, misogynistic, absolute vile banana republic, vile, nasty, Etonian piece of scum.”
But she initially refused to withdraw the remarks, even after leader Sir Keir Starmer distanced himself from them, saying he would “not have used” those words. She later said that her comments were directed at “members of the Cabinet.”
In a statement released today, Ms Rayner said she had “reflected on our political debate and the threats and abuse that now seem to feature all too often”, as well as on her own words at the Brighton gathering.
And she said: “I was angry about where our country is headed and policies that have made life harder for so many people I represent.
“But I would like to unreservedly apologise for the language I used, and I would not use it again.
“I will continue to speak my mind, stand up for Labour values and hold the government to account. But in the future I will be more careful about how I do that and in the language that I choose.”
She added: “All of us in positions of leadership have a responsibility for our language and rhetoric, whether towards political opponents or anyone else in society, especially those already most vulnerable.
“As deputy leader of the Labour Party, I take this responsibility with the utmost seriousness and I am sure that politicians from all parties, the media and others with a prominent role in our public life will also reflect on this shared responsibility.”