A researcher has blown the whistle on Thomas the Tank Engine, saying the classic series is pushing "conservative political ideology" onto kids.

Storylines written for Thomas and his steam-powered friends appeared to "punish individual initiative", the Canadian study found, while female characters were shunted into support roles only.

Political scientist Shauna Wilton, who is an assistant professor in the Department of Social Sciences at University of Alberta's Augustana Campus, said parents should be more mindful of children's programming.

It played a major role in shaping a child's conception of the world and in the case of Thomas the Tank Engine, it was not always constructive.

Dr Wilton said the show conveyed a number of positive political values such as tolerance, listening, communicating with others and contributing to the community.