McNamara is educated by the Irish Christian Brothers at St. Mary’s College, Crosby and he studies for an LLB at the University of Hull. He is head of department in History at St. Mary’s Grammar School (now called St. Mary’s College) in Kingston upon Hull from 1958–64 and a law lecturer at Hull College of Commerce from 1964–66.
After unsuccessfully contesting Bridlington in 1964, McNamara is elected to the House of Commons as Member of Parliament (MP) for Kingston upon Hull North, in a by-election in January 1966 following the death of sitting Labour MP Henry Solomons. Labour’s hold of a former marginal seat with a significantly increased majority is widely considered to have helped to convince Prime Minister Harold Wilson to call the 1966 election to seek a larger majority.
McNamara retains his seat at the 1966 general election, and at subsequent elections until the constituency is abolished for the February 1974 general election, when he transfers to the new Kingston upon Hull Central constituency. When that constituency is abolished for the 1983 election, he is re-elected for the re-created Kingston upon Hull North constituency.
McNamara campaigns in his last years in parliament on many issues, protesting against the Act of Succession which prohibits a Roman Catholic or the spouse of a Roman Catholic to be the British monarch. He steps down at the 2005 general election, with the local Constituency Labour Party choosing Diana Johnson to stand in his place.
During the 2005 general election campaign McNamara claims some of the policies regarding illegal travelers’ sites of the leader of the Conservative Party, Michael Howard, had a “whiff of the gas chambers” about them. Howard’s grandmother died at Auschwitz.
McNamara is known throughout his parliamentary career as a supporter of Irish nationalism and favours a United Ireland. After entering parliament, he soon becomes interested in reports of discrimination against the Catholic minority in Northern Ireland and supports the Campaign for Democracy in Ulster (CDU). He serves as a frontbench spokesman for the Labour Party, including Shadow Secretary of State for Northern Ireland under Neil Kinnock, 1987–94, an appointment that is widely criticised by Unionists.
After Tony Blair becomes Labour leader, he replaces McNamara as Northern Ireland spokesman with Mo Mowlam. In 1997, he helps persuade the newly elected Labour government to donate £5,000 (thereby matching the contribution of the Irish government) for the erection of a memorial in Liverpool to the victims of the Great Irish Famine. He also supports Republicanism in the United Kingdom and joins the All-Party Parliamentary Republic Group.
McNamara is a Roman Catholic and a Knight of the Pontifical Order of Saint Gregory the Great. He is married to Nora McNamara, and is the father of four sons and a daughter.
In 2006, McNamara receives the honorary degree of Doctor of Laws from the University of Hull in recognition of his long service in politics. He graduates with a Ph.D from the University of Liverpool in 2007 having completed a thesis on the MacBride Principles at the Institute of Irish Studies, where he gives the 2008 John Kennedy Lecture in Irish Studies, Perhaps It Will All Go Away – an Examination of the British Response to the Civil Rights Movement in Northern Ireland.