Charges have been laid over a fire stunt that went wrong during the filming of a reality television show.

Occupational Safety and Health launched an investigation after a contestant in Going Straight, made for TV3 by Touchdown Television, caught fire last July.

The man, believed to be in his 20s, was asked to walk through a wall of fire for the second time to get a better shot.

The contestant suffered burns to 12 per cent of his body - mainly his arm and side - and underwent an eight-hour skin graft operation.

He spent a month in hospital recovering.

OSH was alerted to the incident at Wenderholm, north of Auckland, 24-hours later.

An investigation was launched to find out what safety precautions were taken, what went wrong and if there was any breach of the Health and Safety in Employment Act.

An OSH spokesman told the Weekend Herald that charges had been laid over the incident. But he would not comment further until the first court hearing.

The maximum fine for breaching the Health and Safety in Employment Act increased last May from $100,000 to $500,000.

Touchdown Television owner Julie Christie says she has not been told of any charges over the show, which is hosted by Manu Bennett.

"There were six months for charges to be laid and that timeframe expired several weeks ago," Ms Christie said.

"If any charges have been laid, Touchdown has not been informed."

Ms Christie would not comment further regarding fighting the charges.

The production company makes a number of reality and home make-over shows, including Treasure Island, DIY Rescue and Changing Rooms.

The application form for Going Straight says Touchdown may conduct investigations into contestants' background and personal history if they are selected to be on the show.

The injured contestant won the episode and its $10,000 prize.