She is expected to be replaced in her job by Jonathan Azis, a solicitor who joined Hanson as a tax manager three years ago from Beazer, the housebuilding group.
Pro-Ned specialises in finding non-executive directors for public companies. It was founded in 1982 by the Bank of England and later privatised as a joint venture between the headhunting firm Egon Zehnder and its own management.
Ms Newbold, herself a non-executive director at British Telecom since 1991, is joining Pro-Ned after nine years at Hanson.
She qualified as a solicitor while bringing up four children. Her business career began with IBM but she left after the company refused her request for a large pay increase.
Ms Newbold then joined Rank Xerox - spending much of her time on international expansion - followed by three years as European counsel for Walt Disney.
During her time at Hanson, Ms Newbold has camapaigned for the promotion of women in business, using her own success to refute the concept of the glass ceiling.