He served as Senior Government Whip in Norman Kirk's 1972–1975 Government, and colleague Warren Freer said Barclay was an outstanding whip. When Barclay realised that Arthur Faulkner had the votes to win the first ballot for deputy to Bill Rowling in 1974, he got Freer (who was not interested in the position, but who agreed that Faulkner was not leadership material) nominated to split the first ballot vote. They both preferred either Colin Moyle (Barclay) or Bob Tizard (Freer), and Tizard won on the fourth ballot. He was the first Deputy Chairman of Committees (1975). He was unexpectedly defeated in the swing against Labour in the .