"I have tried to hide it but..." Robbie Williams labelled radio host Jackie O a "bad mum" on air.

Radio host Jackie ‘O’ Henderson has been labelled a ‘bad parent’ by pop star Robbie Williams after she revealed she’s a regular smoker.

Making the admission during Wednesday morning’s edition of the Kyle & Jackie O Show, the mum of one told her co-host Kyle Sandilands and guest Robbie Williams, 42, she smokes “probably about 15 to 20 [cigarettes]” every day.

When asked if her five-year-old daughter Kitty knows, Jackie began “I have tried to hide it but…”

It was then that Williams cheekily – and very unnecessarily – called 41-year-old Henderson “bad mum” on air. He also yelled “shame” at her.

Henderson was much too hard on herself in her response.

"It does play on my mind. Every morning I wake up and think, 's**t, should I be doing this because I am a mum now.' So I get the guilt for that reason," she said.

Williams then dived in to share he, too, used to hide his smoking -- from his wife of six years Ayda Field.

"I didn’t tell the missus for five weeks. I was getting up an hour before she would get up, I would creep out of the room with my shoes underneath my arm," he said.

"I would jump through a window at the other end of the house, strip off naked outside, so I wouldn’t smell and then smoke."

Williams added that he went so far as to gargle with hand steriliser instead of mouth wash.

"I was desperate," he said.

And look, just to be clear here, we're not suggesting smoking in front of your child isn't the greatest of ideas. But on the gigantic list of terrible things your children can see you doing as a parent? Well, smoking is pretty low.

A photo posted by Jackie O (@jackieo_official) on Aug 15, 2016 at 2:10am PDT

And if Williams was hoping to encourage Henderson to quit smoking, it's highly unlikely that shaming her on a national scale will help.

If anything, it's likely to stress her out more and have her reaching for another ciggie.

Williams has raised a number of eyebrows since touching down in Australia. Set to appear at the 2016 ARIA Awards on Wednesday night, he playfully told radio host Sam Frost he was disappointed with the way she handled her social media abuse on Tuesday. He then had a seriously awkward conversation about a kiss with The Project's Carrie Bickmore.

Anyone wanting to quit smoking can find information and help at Quit Now.