OTTAWA—Government Senate Leader Marjory LeBreton announced Thursday she is stepping down from her cabinet post.

“While I will be leaving the position of Government Leader in the Senate, I will continue to be an active member of the Conservative Caucus over the next few years,” LeBreton, a Conservative senator for Ontario since 1993, said in a statement Thursday.

LeBreton has been one of the most high-profile figures during the Senate expenses scandal, leading the Conservative response to external reviews of travel and living expenses claimed by Patrick Brazeau, Mike Duffy, Mac Harb and Pamela Wallin.

“I intend to step up my efforts in support of meaningful Senate reform and also actively back the new strengthened rules we introduced regarding Senate expenses,” LeBreton wrote in the statement, where she also thanked Prime Minister Stephen Harper for giving her “the opportunity of a lifetime”.

LeBreton, who first began working for the Conservatives on prime minister John Diefenbaker’s campaign train in 1965, worked for both prime ministers Joe Clark and Brian Mulroney before the latter named her to the Senate 20 years ago.

She worked closely with Harper and travelled with him on his campaign plane during the 2011 federal election.

She is 73 years old Thursday and so set to retire in two years.

Conservative MP Diane Ablonczy (Calgary-Nose Hill), the junior foreign affairs minister for the Americas and consular affairs, also announced Thursday she will not be seeking re-election in 2015.

Ablonczy said the redistribution of electoral boundaries prompted questions about whether and where she would run to keep her seat that she could no longer ignore.

“As I am fully engaged in my responsibilities, I had not intended to publicly share my decision until a year from now. However, since some of my colleagues have recently announced that they will not seek re-election in 2015, the questions are becoming more insistent. That puts me, my family and my staff in an uncomfortable position,” Ablonczy wrote in a statement on her website Thursday.

“I therefore think that, especially since others beside myself are affected, this is the appropriate time to announce that after serving twenty-two years I will be leaving the political arena in2015,” she wrote.

The departures likely mean two more spots Harper will need to fill in the upcoming cabinet shuffle, which the Star’s Tonda MacCharles reported is expected to happen next week.