No matter how many chardonnays you've had, keep off that bouncy castle you hired for the kids' birthday party.

Figures from ACC show injuries relating to inflatable castles have risen by over 60 per cent in the last five years, and the fastest growing demographic is the over-40s.

Children are still the most injured, with 5 to 9 year-olds accounting for more than half of each year's casualty rate. However, in 2008, at least 18 people aged 40-plus registered claims for bouncy-castle-related injuries - last year 31 adults made claims including nine people over 50.

So far this year, at least one person aged over 70 has claimed ACC for a bouncy castle injury.

ACC figures show bouncy castle injury claims cost the country more than $100,000 every year with 2010 a particularly costly year at $212, 816.

Inevitably, experts point the finger at one common denominator: "Don't drink and jump" is the message one Auckland bouncy castle hirer tells his client.

"I can pretty much guarantee alcohol would be involved in at least half those (adult) accidents," the industry veteran said.

Many companies thought bouncy castle staff parties were a good idea but "I've seen the staff go crazy in them," he said.

Another operator said he did not hire to adults as the castles got "thrashed" - "they get cigarette butts in them, get alcohol in them - I don't think bouncy castles should be for adults".

Trudy Hurst from Castlemania Bouncy Castles does hire to adults. She said in 15 years she had not had a single serious accident in one of her castles but claimed some operators hired out castles without proper rules.

Castlemania "put the onus back on them (adults)" with contracts that made the hirer responsible for their own safety.

One operator told the Sunday Star-Times he had seen all sectors of society using bouncy castles - from gang pads to the homes of the Auckland Blues and Kim Dotcom's mansion.

Children appreciated them but: "Adults go too stupid."

THE HIGH COST OF FUN

Year ACC claim:

2008 $123,690

2009 $129,484

2010 $212,816

2011 $111,042

2012 $109,136