Progress in getting women on to the boards of Australia’s top companies has stalled and numbers are in danger of tumbling, new research by the Institute of Company Directors shows.

The proportion of women on boards of companies listed in the benchmark ASX 200 index as of the end of last month was 29.5%, down slightly from 29.7% in December last year.

Over the same time period the rate at which women are appointed has plummeted from 45% of available seats to just 31.7%.

New stockmarket floats have also been reluctant to appoint women, with just 16.6% of board positions filled by women among IPOs last year. And seven top 200 companies, including telco and takeover target TPG, still have no women at all on the board.

“I’m disappointed by the loss of momentum – by the end of 2018, we really thought we had good momentum, I’m surprised by this outcome,” the AICD chief executive, Angus Armour, said.

He said the AICD’s regular survey of company director sentiment showed the worst picture since 2015.

“It’s quite a significant drop from where we were a year ago, a year and a half ago,” he said. “And I suppose people in that environment start becoming more conservative, they pull back into the network that they know, they try to pull together people they feel are going to have the benefit of experience.

“They’re hiring former CEOs, which at this point are mostly men. But they also need to ask themselves whether some of these challenges might be better met by having a more diverse set of opinions around the board table.”

He said the seven ASX200 companies with no women on the board – TPG, Pro Medicus, Polynovo, NRW Holdings, Silver Lake Resources, HUB24 and Speedcast International – “stand out in a really negative way”.

“I’m surprised that they’re not interested in the message,” he said. “If they hold themselves up relative to the ASX50 or the ASX20, any of these seven companies look up and say, ‘Wow, are we performing as well as the best companies in the index?’ they’d have to say no.”

He said research showing companies with at least one woman on the board performed better was “robust”.

“Having diversity in any decision making unit … increases the likelihood of better outcomes,” he said. “Groupthink is not a new term. It is decades old.”