The former war memorial director was appointed to fill a vacancy left by retiring chair and long-serving member Kerry Stokes on Tuesday.

Veterans' Affairs Minister Andrew Gee announced the decision, which would allow Dr Nelson to serve through the institution's controversial $500-million redevelopment plans.

"In the seven years Dr Nelson was director of the Australian War Memorial he worked tirelessly to ensure it remained at the forefront of our nation's story of service and sacrifice," the minister said in a statement.

"His long history of service to the Australian people as a medical practitioner, member of the Australian Parliament, diplomat and business leader will also bring a wealth of experience to the council.

"Our war memorial is sacred to Australians as a place of solemn reflection and pride in our nation's history of service. Generations of Australians have a special connection and bond to it through their own story of service and sacrifice or that of their family. I am very pleased Dr Nelson will again bring his passion and energy to it."

Dr Nelson served as the war memorial's director between 2012 and 2019 and was briefly a Liberal Party opposition leader and a defence minister in the Howard government prior to the role.

Billionaire businessman Kerry Stokes, who has been the council's chair for six years, will vacate the seat he's held as a member for 15 years.

Mr Gee thanked Mr Stokes for the "critical role" he played in developing the nationally significant memorial.

The council will soon vote a replacement to take over the role of chair.

Mr Stokes remained supportive of a major 10-year plan to overhaul the institution, creating additional space for new exhibits.

The former chair slammed eminent critics who opposed the $500-million proposal and said they'd only raised their voice after designs were released.

Heritage council experts and former memorial historians formed a group of voices who wanted to see the plans drafted in a more consultative form.

"Only after the final designs came out did the special interest groups seem to gather their momentum," Mr Stokes said.

"And most of those are in Canberra. We will not satisfy every single person.

"The number of people who claim not to have been involved is very small."