In these positions he supported successive New South Wales Labor leaders such as Pat Hills, Neville Wran and Barrie Unsworth (also a Catholic convert).
[citation needed] According to historian C. J. Coventry, Ducker was a "prolific informer" for the United States of American throughout the 1970s, providing inside-information about the Labor Party and the ACTU.
For example, when Frank Sinatra insulted women journalists, causing a nationwide boycott of the singer, Ducker worked with the Ambassador and ACTU President Bob Hawke to bring about a quick resolution.
In 1979, Ducker's health declined and he resigned all his official positions, but Wran appointed him chairman of the New South Wales Public Service Board.
He remained a powerful influence behind the scenes, supporting younger Labor leaders such as Graham Richardson, Bob Carr and Paul Keating.