A leading researcher has quit his role overseeing a parenting support programme in use across Glasgow.

Professor Phil Wilson, visiting professor at Glasgow University and director of Aberdeen University's centre for rural health, was the lead author of a report published earlier this month that evaluated the Triple P parenting programme.

The report, which cost £190,000, concluded the system on which NHS Greater Glasgow and Clyde has spent at least £4 million, has had minimal impact and said the health board should pull out of funding it.

A large drop-out rate, especially among the most needy families, meant results were limited, while the social and emotional functioning of the children who did complete it did not improve, said the report.

However, the health board rejected the research as "flawed" and published criticism of the way it had been carried out, saying it "lacked credibility". Now Mr Wilson has resigned from a group that had been exploring using the Triple P methods with expectant parents.

He has written a stinging letter to Dr Linda de Caestecker, the city's director of public health who is chairwoman of the Triple P for Baby Trial steering group.

He says Professor Matt Sanders, founder of Triple P, was allowed to contribute to criticism of his team's research, which he describes as "unacceptable practice." Meanwhile Dr De Caestecker has appeared in promotional material advertising Triple P around the globe, he says.

Mr Wilson also argues the statement issued by the board in response to the report was inaccurate and offensive. He adds to Dr De Caestecker: "Your personal comment that we lack understanding of the way families live their lives in Glasgow was deeply insulting to someone who has worked as a GP in the city for 24 years."

Simultaneously, Mr Wilson has written to Robert Calderwood, the health board's chief executive, raising a series of questions about Triple P. Both letters were copied to figures in the academic and public health community, while the resignation letter to Dr De Caestecker was also copied to new Scottish Health Minister Shona Robison.

Mr Wilson has asked Mr Calderwood to explain why the decision to sign a contract with Triple P International in 2010 was not subject to normal procurement processes.

He also queries Dr De Caestecker's role. "I am concerned her bias in favour of Triple P ... has led the board to act unwisely and extravagantly," he says. He also asks why the health board helped establish a chair at Glasgow Caledonian University to allow Professor Sanders, who still benefits financially from Triple P, to conduct research on his own programme in the city.

Finally, he asks Mr Calderwood why the board has rejected his team's research. "There is no other plausible explanation for this ... save that [NHSGGC] did not like the findings in the evaluation report," he says.

A health board spokeswoman said Mr Calderwood had only received his letter on Wednesday and would respond to the issues raised by Professor Wilson and give an "accurate" account of the board's actions in due course.

"Until we have had time to prepare our response and provide the correct description of these issues it would be inappropriate to comment," she said.