He was first elected to the House of Commons of Canada in the 1962 election, and served continuously as a Member of Parliament (MP) for Hamilton, Ontario in the electoral riding of Hamilton East until his resignation in 1984, following his defeat for the leadership of the Liberal Party of Canada which was eventually won by John Turner.
from Osgoode Hall, Munro entered politics as an alderman for Hamilton, Ontario City Council in 1954.
[citation needed] Munro was first elected to the House of Commons in 1962, representing the riding of Hamilton East.
[citation needed] On June 21, 1981, the Toronto Sun ran a front-page story accusing Munro of profiting from illegal insider trading through his advance knowledge of Petro-Canada's bid to acquire Petrofina Canada.
Even with the Sun's retraction and apology, the paper was ordered to pay Munro $75,000, then a very high award for a libel case in Canada.
[citation needed] On June 27, 1978, Munro married future David Peterson Cabinet Minister Lilly Oddie, who took his surname.
Munro attempted to return to Parliament in the 1988 general election in the riding of Lincoln but was defeated by Progressive Conservative Shirley Martin.