Emily Blatch, 67, was education minister between 1992 and 1994 and was later shadow education minister in the Lords when Labour won the 1997 election.
Michael Howard, the Conservative party leader, this week led tributes to his former colleague.
He said: "Emily was a wonderful friend and a fantastic colleague. She was loyal and dedicated. She worked throughout her career to help people less fortunate than she was.
"I will miss her enormously, as will the Conservative party and the House of Lords."
Sir Bob Balchin, former chairman of the Grant-Maintained Schools Foundation, who worked with Lady Blatch on setting up the sector, said:
"Emily Blatch was the best of all the education ministers I have worked with. She was extremely courageous and stood no truck with difficult civil servants. She always stood by her principles and was entirely straight.
People will remember her for the wonderful, supportive relationships she had with others."
Lady Blatch was a campaigner for the protection of children and took a keen interest in their educational needs. She supported the retention of Section 28 of the Local Government Act, banning the promotion of homosexuality in schools.
She was a former leader of Cambridgeshire county council and had served in the Women's Royal Air Force and the civilian branch of Air Traffic Control during the 1950s. She later became a member of the Peterborough Development Corporation.
She was ennobled in 1987, and then held office as a front-bench spokesman in the Lords in John Major's government. She was promoted from her shadow education brief in 2000 to deputy Opposition leader in the Lords.
In 2003 she was named "Peer of the Year" in the BBC's Parliamentary awards.
While in the Lords she became known for her frequent exchanges with Baroness Blackstone on educational matters, including teacher shortages and the creation of a general teaching council.
She had, until recently, continued to attend the House of Lords.
She married John Blatch in 1963 and had a son, a twin son and daughter and a third son, who later died.