Australia’s airports are concerned that fewer domestic seats and an airline duopoly is leading to higher prices for travellers.

A report by the Bureau of Infrastructure, Transport and Regional Economics found there were at least 85,000 fewer seats available for domestic passengers in the year to March 2018 compared to two years before.

This is despite passenger numbers growing by 2.4 million over the same period.

Australian Airports Association CEO Caroline Wilkie on Friday said the trends were “deeply concerning”.

Speaking on behalf of the country’s airports, Ms Wilkie said she was disappointed the report also found domestic airfares increased by 13.3 per cent over the same period.

“Fewer domestic seats and higher airfares will constrain tourism and broader economic growth, forcing passengers to pay more,” she said in a statement.

Ms Wilkie said Qantas and Jetstar earn about 90 per cent of the total domestic airline profit pool, which is a “real source of market power”.

“Interestingly, the picture in international aviation is far different, with strong competition from international carriers driving more capacity and cheaper fares than ever before,” Ms Wilkie said.