A former Garda Detective Inspector says there was a culture of "squaring" away minor road traffic offences by Gardaí when he was in the force and it ran from the top down.

Gerry O'Carroll made the comments following calls by 4 independent TDs for an independent investigation into allegations that 66,000 traffic offences were quashed by senior Gardaí in the last 4 years.

The Minister for Justice Alan Shatter said last week he was concerned that politicians and media coverage may prejudice an investigation into the quashing of tens of thousands of penalty points.

Mr. Shatter told the Dáil he had received an interim report and there may be nothing inappropriate about the quashing of points.

He said while he is taking the issue seriously, early signals are that in some cases there was nothing untoward with what went on.

"Part of a culture"

Meanwhile the Garda Commissioner Martin Callinan confirmed a "vigorous and comprehensive investigation" was underway into the quashing claims.

He said any allegations of impropriety against members of the force was a matter of huge concern to him but he added any wrong doing would be highlighted in Assistant Commissioner John O'Mahoney's internal investigation.

Mr. O'Carroll is now a columnist with the Evening Herald.

He told Breakfast here on Newstalk it was common practice when he was a Garda but only for minor offences.

While speaking in the Dail ULA TD Clare Daly said the claims have been downplayed.