Hopeful take shelter as they prepare to audition for Soapstars
The union has called the fly-on-the-wall show, in which contestants compete to star in a soap opera, an "insulting affront" to the actors.
Soapstars is a follow-up to the successful Popstars programme, which launched the band Hear'Say.
But Equity says the programme is deameaning to their members.
In a statement, the union's governing council said the series was "an insulting affront to the men and women in our profession who endure low rates of pay, rejection and humiliation in the course of their work, despite their training, experience, dedication and talent".
Soapstars, which forms part of the new autumn and winter schedules on ITV1 began on Monday.
Familiy
It has already attracted thousands of would-be soap actors and actresses to regional auditions.
The winners will take on the role of a new family in the award-winning drama Emmerdale.
Equity Council member and former Emmerdale cast member Jean Rodgers, said: "Most performers are in the business because they want to entertain, inform and enrich the culture of the country, not to be `rich and famous'."
She played Dolly Skilbeck in the soap opera.
Colin Tarrant, Inspector Monroe in The Bill, who is also a member of Equity Council, said the docusoap encouraged "stereotypical misconceptions" about the acting profession.
Soapstars attracted thousands of hopefuls to auditions for the show.
Many queued for up to 14 hours in order to appear before the judges, who are looking for five people to play the new family members.