An investigation has been launched after passport office staff deemed that acting was "not a proper job".
Michael Sheldon, who is appearing in the West End production of Three Days in May, countersigned a passport application for his daughter's boyfriend which was rejected after staff told him Sheldon was not regarded as an acceptable referee.
Malcolm Sinclair, president of the actor's union Equity, wrote to Home Secretary Theresa May, saying that to be told acting was "not a proper job" was "simply unacceptable".
He told The Stage newspaper the rejection was "staggering and something I felt I had to challenge".
"Unless we are told otherwise, we must take it that the views of a clerk in the passport office represent those of the Government," he said.
"If it is the Government's opinion that 'acting is not a proper job' then I think they should come out with it."
He added that the comments had caused some Equity members "dismay, even outrage".
The passport application was also rejected due to an unsuitable photograph.
A spokesman for the Identity and Passport Service (IPS) said: "We will be investigating and looking at whether further staff training is required. We provide a list of occupations solely as a guide to assist customers.
"The occupation of the counter-signatory is not a determining factor in considering a passport application. We will make that clear on the Direct.Gov website."