The Transport Agency's urging owners of heavy vehicles checked by a dodgy certifier, to have them looked at again.

The safety of towing connections of almost 500 trucks, trailers, buses and motorhomes could have been falsely certified by Richard "Dick" Joyce, who operated around Wellington and Wairarapa.

He's been suspended indefinitely following an investigation.

About half of the vehicles are around Wellington and Wairarapa.

Road Transport Forum chief executive Ken Shirley told Mike Hosking he is supporting the call and says it's about critical safety.

"Over the years, some were just cutting corners, were doing things from photographs and weren't actually seeing the product necessarily so some of the connections were too old or too weak."

LISTEN ABOVE AS KEN SHIRLEY SPEAKS WITH MIKE HOSKING