Veteran News Corp columnist Piers Akerman has rejected criticism directed at him for joining former prime minister Tony Abbott on the campaign trail in his seat of Warringah on the weekend.

Former Sydney Morning Herald and The Age journalist Mark Kenny said on the ABC's Insiders on Sunday morning that "a lot of people are looking at this thinking: 'This surely crosses a line.' "

Piers Akerman donned an Abbott shirt but said he had spent most of the day patting dogs standing in the background. Credit:Tony Abbott/Instagram

Akerman - who was wearing a "Tony Abbott for Warringah" T-shirt - rejected that, saying he was there as an "independent Australian and a private citizen".

He said there was no more conflict between him joining Mr Abbott and working as an independent commentator than there was for ABC journalists who drove with Mr Abbott's opponent, Zali Steggall, for a story on 7.30 to the press conference at which she announced her candidacy.