LOS ANGELES – Hollywood labor unions are stepping up their dispute with production companies behind TV reality show "The Biggest Loser", calling for picket lines on Monday to confront replacement workers hired last week.

The 50-member crew of the NBC show has been on strike since last week, seeking a union contract primarily in order to obtain pension and health benefits. The picketing was initially low-key, starting with just a dozen picketers on Wednesday and growing by the end of the week to several dozen.

Monday may be much larger. This time, the International Alliance of Theatrical Stage Employees (IATSE) said in a statement that picket lines will be mounted at the production location in rural Calabasas, outside Los Angeles.

The start time and duration of picketing were not released.

"The crew has not lost their resolve in spite of the employer hiring replacement workers and being unwilling to discuss a contract. The IATSE will not lose our resolve to support them until this strike is over," IATSE international president Matthew D. Loeb said.

In the statement, IATSE said the strike started last Monday, and that it has had no talks since Tuesday with the production entities.

The "Biggest Loser" production crew voted 100 percent to support the labor union. According to IATSE, the producers refuse to recognize the labor union as the bargaining unit for the crew. The TV performers union AFTRA and the Directors Guild of America (DGA) already have agreements with the show.

The production entities and AFTRA could not be reached for comment, and the DGA declined to comment.