The veteran Nova Scotia MP has held several senior cabinet positions since the Conservatives took power in 2006, including foreign affairs and defence, after serving as the last leader of the now-defunct Progressive Conservative Party.
- Photos: Standard-bearer for former PCs stepping aside
He joins other high-profile Conservatives who have left, or have announced they are leaving, federal politics.
Former foreign affairs minister John Baird stepped down as MP for Ottawa West-Nepean this past March. His 20-year political career began as an Ontario MPP before he was elected federally in 2006.
International Development Minister Christian Paradis announced in April he will not seek re-election for the Quebec riding of Mégantic-L'Érable. Since he was first elected in 2006, he has held several cabinet positions, including minister of public works and government services, minister of natural resources and minister of industry.
Heritage Minister Shelly Glover also announced in April that she will not seek re-election for the Winnipeg riding of St. Boniface. She was first elected in 2008.
Calgary MP Diane Ablonczy will not run after more than 20 years representing the Reform, Canadian Alliance and Conservative parties in the House. Under Harper, she has filled various roles, including minister of state of foreign affairs (Americas and consular affairs), minister of state for seniors, minister of state for small business and tourism and parliamentary secretary to the minister of finance.
Gordon O'Connor, who has been MP for the Ontario riding of Carleton-Mississippi Mills since 2004, is not running in the next election. He held various positions between 2006 and 2013, including minister of national defence, minister of national revenue and chief government whip.
Barrie MP Patrick Brown resigned this spring after winning the leadership in of the Ontario PC party. Alberta MP Brian Jean also resigned last year to run, successfully, for the leadership of Alberta's Wildrose Party.
Other Conservative MPs not seeking re-election
British Columbia- Dick Harris was first elected in 1993. He has represented the Reform and Canadian Alliance parties, and currently holds the riding of Cariboo-Prince George for the Conservatives.
- Russ Hiebert has represented South Surrey-White Rock-Cloverdale since 2004.
- Colin Mayes has represented the riding of Okanagan-Shuswap since 2006.
- James Lunney left the Conservative caucus earlier this year to defend his "freedom of religion." He had previously announced he would not seek re-election for Nanaimo-Alberni. He was first elected in 2000 as a member of the Canadian Alliance.
Alberta- Rob Anders has represented the riding of Calgary West since 1997. He was first elected as a Reform MP, then a Canadian Alliance MP.
- Peter Goldring has represented the riding of Edmonton East since 1997. He was first elected as a Reform MP, then a Canadian Alliance MP.
- Laurie Hawn has represented the riding of Edmonton Centre riding since 2006.
- Brian Storseth has represented the riding of Westlock-St. Paul since 2006.
- LaVar Payne has represented Medicine Hat since 2008.
Saskatchewan- Garry Breitkreuz was first elected in 1993. He has represented the Reform and Canadian Alliance parties, and currently holds the riding of Yorkton-Melville.
- Maurice Vellacott was first elected to the House of Commons in 1997 as a Reform MP for the Saskatchewan riding of Wanuskewin. He currently holds the Conservative seat for the riding of Saskatoon-Wanuskewin.
- Ed Komarnicki has represented Souris-Moose Mountain since 2004.
- Ray Boughen has represented the riding of Palliser since 2008.
Manitoba- Manitoba MP Joy Smith has represented the Winnipeg riding of Kildonan St. Paul since 2004.
- Manitoba MP Rod Bruinooge has represented the riding of Winnipeg South since 2006.
Ontario- Gary Schellenberger, who currently represents Perth-Wellington, was first elected in a 2003 by-election.
- Joe Preston has represented Elgin-Middlesex-London since 2004.
- Barry Devolin has represented Haliburton-Kawartha Lakes-Brock since 2004.
- Patricia Davidson has represented Sarnia-Lambton since 2004.
- Rick Norlock has represented Northumberland—Quinte West since 2006.
New Brunswick- Mike Allen has represented Tobique-Mactaquac since 2006.
Nova Scotia- Gerald Keddy was first elected to the House of Commons in 1997 as a Progressive Conservative. He has represented South Shore-St Margaret's since 2004, after previously holding the seat for the riding of South Shore.
- Greg Kerr has represented West Nova since 2008.