Katherine Victoria Newton was born to farming parents at Te Mata, on the West Coast of the North Island and attended Hamilton Girls' High School.
[citation needed] O'Regan was a voting delegate for the National Party in the Raglan electorate candidate selection ahead of the 1975 election, where she supported Marilyn Waring.
As Associate Minister of Health, she amended the Human Rights Act to outlaw discrimination on the grounds of sexual orientation and having organisms in the body which might cause disease and established a free breast cancer screening programme.
[4] With the National Party forming a coalition government with New Zealand First, O'Regan did not continue as a minister and was instead appointed the Chairperson of the Internal Affairs select committee from 1996 to 1999.
[7] In the 1999 general election, she again challenged Peters, and came within 62 votes of defeating him—had she won, the New Zealand First party would have lost all parliamentary representation.
She favoured compulsory sex education from age ten and condom vending machines in all secondary schools and public toilets.
[13] In an obituary, her daughter Susan O'Regan described her mother as a Royalist, feminist, and strong believer in equal rights.
O'Regan was diagnosed, through the free screening programme she had established as Associate Minister of Health, with breast cancer in 2008.