He was Parliamentary Private Secretary to Judith Hart, the Paymaster-General, and served as Parliamentary Under-Secretary of State for Scotland during the 1974–1979 Labour government, dealing with home affairs, housing and agriculture and fisheries. After Iceland expanded its claimed fishing territory to 200 nautical miles, Brown joined the MP for Grimsby, Tony Crosland, as British negotiator with Iceland during the third Cod War, in 1976–77. Brown was praised for the role he played in resolving the dispute both by the Prime Minister, Harold Wilson, and by the Icelandic Government.