ACTU secretary Sally McManus has accused the ABC of refusing to let her on the premises of the public broadcaster for a talk to union members on Wednesday.

In an astonishing tweet, McManus said the ABC was "the first employer in the country to say 'no' to me being allowed on their premises to talk to their employees" since she was elected in March last year.

ACTU Secretary Sally McManus says she hopes the ABC refusal to allow her on its premises is a 'misunderstanding'. Credit:Alex Ellinghausen

The leader of Australia's union peak body said she had visited "many, many workplaces across the country - maybe one a week" in her time in the role, including "factories, building sites, offices, casinos, schools, hospitals, yards and workshops".

"In every case, the employer has been happy to have me visit," Ms McManus said.