The Wheat Growers Action Group has complained that the four grower directors opposing the removal of grower marketing rights have been silenced through "the threat of legal action and the failure of AWB management to provide them with logistical support to attend scheduled meetings".

"That is completely unfair and totally unacceptable," Sen Nash said.

"Growers deserve to be fully informed of all views regarding this issue."

Sen Nash and Mr Cobb are backing WGAG's demands for AWB to provide the resources to allow all directors to attend the remaining grower meetings across Australia.

The grower meetings conclude on August 7, the deadline for postal and online voting is August 19, and the extraordinary general meeting will be held in Melbourne on August 21.

"There is not going to be a fair outcome unless there is a fair process with fair representation for growers," Mr Cobb said.