The Tory peer sparked outrage last year when she was among 272 Lords who voted in favour of former Chancellor George Osborne’s plan.
The businesswoman, who was appointed Baroness Mone of Mayfair by former PM David Cameron, then further infuriated low-income families in the wake of the vote by tweeting: “If you really want something, really work hard, don’t look for excuses, be proactive, have a can do attitude and never ever give up, you will succeed.”
However Mone, 45, has now expressed her regret over backing the plans not to delay the cuts, which would have cost three million struggling families £1,300 a year had they not been blocked by Labour peers.
During an online question and answer session, Mone was asked by Twitter user Jack Reason: “Why did you use your first vote in the House of Lords to support working tax credit cuts?”
She replied: “It was a mistake and I regret it.”
Following the row over tax credits, the Ultimo founder wrote a tweet, which was later deleted, defending her decision not to oppose the government plans.
She wrote: “Under a long-standing Parliamentary convention the House of Lords does not block any government measure concerning the nation’s finances.
“This is because peers are unelected and have no right to reject measures to do with tax and spending which have the support of MPs chosen by the public.”
A few days after the vote Mone was photographed at the exclusive Sandy Lane resort in Barbados with her ex-boyfriend Stefan Soroka, a golf coach.
Mone, who joined the Lords on September 30 last year, was later ridiculed for quoting lyrics from a Whitney Houston song in her maiden speech to show support the youth of the country.
She recited lines from The Greatest Love of All, saying: “I normally sing this at karaoke - I believe the children are our future, teach them well and let them lead the way.”
Last year, senior Scottish business figures questioned her business acumen when Mr Cameron invited her to lead a study into ways to encourage start-up businesses in disadvantaged areas.
The appointment coincided with news she was being made a Tory peer. She faced further criticism when pictures emerged of her using a chauffeur-driven government car to undertake her review.
Mone, a former Labour supporter, grew up in Glasgow and left school at 15 before setting up lingerie giant Ultimo in 1996 with ex-husband Michael. The pair split acrimoniously in 2012.