He was a member of the Australian Labor Party (ALP) and served in federal parliament from 1969 to 1990, representing the Division of Robertson in New South Wales.

His paternal grandparents were Polish Jews from the villages of Pajęczno and Działoszyn, who immigrated to Australia via England and South Africa; other members of the family who remained in Poland were killed in the Holocaust.

[2] He was president of the St Ives Merchants' Association and in 1965 led a protest calling on the state government to extend shopping hours.

In 1970 he criticised the Gorton government for adopting a "neutral" stance in the Israeli–Palestinian conflict and accused the Arab lobby in Australia of using Nazi propaganda tactics.

[6] Cohen was elected to Bill Hayden's shadow ministry in 1977 and named opposition spokesman for the environment, sport and recreation, tourism and home affairs.

[1] On 11 March 1983, following the ALP's victory at the 1983 federal election, Cohen was appointed Minister for Home Affairs and the Environment in the Hawke government.

[citation needed] After leaving parliament, Cohen remained active as a political commentator, writing columns for The Australian and The Bulletin.

[19] Cohen was appointed a Member of the Order of Australia in the Queen's Birthday Honours in 2007, for service to the Australian Parliament and to the community through a range of cultural and environmental roles and contributions to public discussion and debate.