In a new twist in the debate over Federal Labor's union ties, Liberal frontbencher Tony Abbott has described his background in the union movement.

Mr Abbott has come out saying he used the support of a union when he was a journalist.

"I was a union member for a while when I was a journalist, I was a member of the Australian Journalists' Association," he said.

"In fact I moved a resolution to go on strike one day after consolidated press management sacked the whole photographic department."

The Labor Party has since seized on Mr Abbott's admissions amongst intense scrutiny from the Coalition in a recently unveiled advertising campaign.

Labor's health spokeswoman Nicola Roxon says Mr Abbott's union background highlights how silly the advertisements are.

Treasurer Peter Costello has admitted that the Coalition wrongly named some Labor MPs as former union officials in a recent advertisement.