"This is completely absurd," said Unite national director Mike Treen.
"Since when does carrying a Bible in your pocket become unlawful in New Zealand workplaces?"
Grainne Troute, SkyCity general manager group services, called the union's response "alarmist" and said a breach of uniform policies was unlikely to result in a sacking.
"Different roles have different uniform standards but as a general principle staff in customer service roles are in breach of SkyCity's uniform standards if they carry items such as mobile phones, books and other items which might interfere with their full engagement with their customers."
She said such a breach of uniform policies was not considered serious misconduct and would not be expected to result in the dismissal of any staff member.
In a letter to Ms Parata last Tuesday, the casino said: "The company is considering disciplinary action being taken in relation to the alleged incident on April 26 2012 when you were seen by a senior manager of another department with non-work related material in a front of house work environment."
An earlier letter of May 27 related how a manager saw Ms Parata with the Bible in toilets and how a union rep told her it didn't matter if it was "a Playboy magazine or a Bible, it was not work related material, therefore should not be with you front of house and certainly not being read".
Ms Parata said today that carrying a Bible at all times was a vital part of her faith and relationship to God.
She was reluctant to comment further, saying: "I'd rather wait til after Thursday's meeting."
Unite, which has 8000 members across several sectors in New Zealand, including 700 - 800 at Skycity, said it had already tried to argue for their member but the casino seemed unmoved.
"We tried to explain that a business that feeds off gambling addictions of many people in this country and is seen as a den of inequity already won't do its reputation any good. However, our efforts fell on deaf ears."
He accepted that the casino needed strict rules over dealers and workers handling money and what they could carry on them but said the policy went "overboard".
"What happened to freedom of opinion and religion as guaranteed by the Bill of Rights?
"It gets to the point where the bureaucratic rigidity rides over practical common sense.
"We do not believe that ordering staff not to carry a pocket Bible is a lawful or reasonable instruction in a workplace in the 21st century."
