Radio and television personality Chrissie Swan has made a tearful on-air confession, admitting to smoking while pregnant.

The former Circle host and Mix FM presenter's came clean during a segment on her Melbourne radio show Chrissie and Jane this morning.

The star was recently snapped by a photographer having a secret puff in her car.

"I've struggled terribly with totally giving up cigarettes since I found out I was pregnant," she admitted.

"Up until about six years ago I was what you call a full-time smoker.

"I really gave it a nudge in my 20s, as a lot of us did.

"Then I met 'the Chippie' (husband Chris) who has never smoked and I cut back a lot...then I got pregnant with Leo and I quit completely for a couple of years, which was fantastic.

"Now sadly, I picked it up about a year ago and I was what I would call a 'not really smoker'.

"I never smoked at home and I never smoked around my family. I'd just sneak a few here and there, and I know I'm not alone in this. Mainly I would do it in the car, in fact, I would only do it in the car when I was certain that I was alone."

Swan discovered she was pregnant for the third time six months ago, and says the news came as a 'massive surprise'.

She said she attempted to go 'cold turkey' and stub out the smokes completely but admitted she failed time and time again.

"I was confident I could do it, but I just couldn't," she said.

This morning's tell-all has sparked public backlash - preempted by Swan who recently removed her Twitter page.

But anti-smoking groups say Swan's admissions about her serious battle with nicotine addiction could inspire others to address theirs.

Quit Victoria executive director Fiona Sharkey said: "It's harder than alcohol, it's harder than cocaine to give up. It is very, very addictive. This will help thousands of others to say they are not alone."