Manufacturers are developing "large numbers" of new drugs that offer few clinical advantages to boost profits, a BMJ article has claimed.

The article, written by professors in psychiatry and health policy in New Jersey and Toronto, accused pharmaceutical companies of exaggerating research and development costs for new drugs. It argued that most research costs went towards developing "scores of minor variations" on existing drugs and cited research that found up to 90 per cent of new drugs in the past 50 years had provided "few benefits and considerable harms".

Opinion is divided over whether the pharmaceutical industry is putting profits before patient benefits

More news on drug development ABPI hits out at value-based pricing UK patients will suffer if drug discovery not rewarded, warns ABPI chief Value-based pricing gets go-ahead, DH confirms

The Association of the British Pharmaceutical Industry (ABPI) slammed the claims, stressing the "incremental improvements" made in areas such as HIV treatment. It added that the regulation around bringing a drug to market was becoming "more onerous", with the average drug now costing more than £1 billion to develop. But the article published on bmj.com said pharmaceutical companies spent far more of their profits on promoting drugs than conducting research. And it also hit out at the belief there was an "innovation crisis" in the pharmaceutical industry.

This only served as a "ploy to attract a range of government protections from free market competition", said the study's authors, Professor Donald Light at the University of Medicine and Dentistry of New Jersey and Professor Joel Lexchin of York University, Toronto.

And the authors called on governments to stop funding new drugs that had little therapeutic benefit – appearing to support the principles of value-based pricing. "EU countries are paying billions more than necessary for drugs that provide little health gain because prices are not being set to reward new drugs in proportion to their clinical value," they said.

But Stephen Whitehead, chief executive of the ABPI, defended policies to reward smaller drug developments. "Medical research has always rested on iterative and gradual innovation rather than breakthrough advances, which are very rare," he said.

And despite the "promising" pipeline of new medicines, discovery was becoming more difficult, Mr Whitehead argued. "The discovery of medicines is an increasingly difficult process as the cost of research and development continues to rise and regulation becomes more onerous," he said. "In 2012, it costs on average over £1 billion to develop a new medicine and takes between 12 and 15 years to develop."