Ms Creighton said she handed in her letter of resignation last night following a direct instruction from Enda Kenny.
The instruction almost immediately followed her decision to vote against the Government during the debate on the controversial abortion bill.
"I had already lost the whip of the party so the consequences were pretty apparent to me and I didn't really want to drag it out. The Taoiseach asked me this evening (to resign) and I responded," she said, following the vote.
"I spoke to him at length last Monday when we were travelling to Strasbourg together and I had a chance then to basically tell him my continued concerns about the legislation," she told TV3's Tonight With Vincent Browne.
Ms Creighton last night withdrew one of her amendments during the debate and voted against the Government. She was automatically expelled from the parliamentary party and lost the Fine Gael whip.
Ms Creighton watched on as some of her own Fine Gael colleagues told her she was "wrong". She claimed some TDs were confused by her amendment – which related to the imposition of abortion time limits where a foetus is viable.
"We know that in the vast majority of jurisdictions around the world where there are abortion regimes in place, far more liberal regimes of the type I hope we never see in this country, they do still enforce gestational limits for carrying out abortions," the Dublin South East TD told the Dail. "I think that this is the minimum our citizens deserve."
At one point during the debate, she rolled her eyes when challenged by Fine Gael TD for Kildare, Bernard Durkan.
The debate itself will go down as one of the most memorable in Dail history. A last-minute attempt to block the vote in the courts was dismissed by High Court President Nicholas Kearns.
The challenge was taken by a group which includes former MEP Kathy Sinnott and was supported by Tipperary TD Mattie McGrath.
Justice Kearns said the bill was already on the floor of Leinster House and he did not have jurisdiction to interfere.
Meanwhile, a Government TD missed an early morning vote on the contentious abortion bill – but has insisted that it was a mistake.
Fine Gael TD for Limerick, Dan Neville did not vote on an amendment regarding fatal foetal abnormality tabled by the Dail technical group.
Mr Neville said that he wasn't asleep before the vote but said it was very late and the doors to the chamber had closed before he could enter and vote.
A Labour TD was left red-faced after he mistakenly voted the wrong way on the same amendment.
Clare TD Michael McNamara voted with the opposition on the amendment. However his party whip Emmet Stagg later explained that this too was a mistake.