The Fair Work Ombudsman is investigating the Church of Scientology over allegations it has grossly underpaid staff members.

A number of former employees of the church have told ABC's Lateline they were only paid a few thousand dollars per year for full-time work and had to resort to welfare payments to survive.

Janette Lang, who worked for the church for seven years, says the most she was paid in a year was $3,114 in 2001.

She was second in charge of the Church of Scientology in Canberra at the time.

Ms Lang told Lateline it was "awful".

"Trying to survive as a staff member was a constant battle," she said.

Ms Lang says she had to go on welfare to get by. She says this practice was widespread in the church.

The Church of Scientology declined Lateline's request for an interview, but in a written statement said: "the Church denies any widespread use of welfare by its staff members. Her allegations are unfounded and false."

Lateline has spoken to seven ex-scientologists who say they were on welfare while working full-time for the church.

One former member says she and six other staff members were on the dole while working for Scientology in Melbourne in the 1990s.

Paul Schofield worked for various Scientology organisations in Australia for over 20 years.

He says he had to rely on part-time work and welfare to support his family.

"I didn't even have enough money for petrol to get to work. I had no money for nappies for my daughter," he said.

"I had no money for dog food, yet I was being harassed to come to work and work for nothing."

Tommy Davis, a spokesman for the Church of Scientology in the United States, told ABC's Four Corners in February that staff across the world are paid a living wage.

"General church staff who may work in a church or temple in Sydney or Melbourne or Los Angeles or Cincinnati, wherever it may be in Europe or Asia, they would then have a living wage," he said.

But Dean Detheridge, a former staff member of 17 years standing, denies Mr Davis' claims.

He says he never earned more than $5,000 dollars per year and rarely got holidays.

"In the first 11 years when I was on a full-time schedule I took four days off - they were two weekends and that was difficult to get approval for," he said.

Allegations like these - that are now being investigated by the Fair Work Ombudsman - were prompted by the Four Corners program earlier this year.

'Volunteer' work

Former Scientologists believe the investigation could lead to massive claims for back-pay.

"I personally believe it could bankrupt them," Ms Lang told Lateline.

Ms Lang estimates she could be owed $250,000 in wages. Mr Schofield says his back-pay could be worth $750,000.

Dean Detheridge, who was an executive in the church, says he would have forgone over $1 million in wages.

But the Church of Scientology claims people who sign up to work do so as volunteers.

"Our Church staff are volunteers and understand this and are not helping for the purpose of financial gain," the church said in a written statement.

But the former Scientologists Lateline spoke to deny that all staff are volunteers.

"When I wanted to leave at 2:00 am with my two little girls I was not given the choice to leave," Ms Lang said.

"I would beg to leave and still be told no. There were consequences if you chose to go against what you were being told to do. These people are not volunteers."

Ms Lang and Mr Schofield have given evidence to the Office of the Fair Work Ombudsman. Their investigation continues.

Read the statement and a revised statement from the Church of Scientology.