Construction of Perth's Elizabeth Quay is slashing customer numbers at Barrack Square businesses but they're not being fairly compensated by the state government.

The noise, pedestrian diversions and general construction mess is proving a turn-off for patrons, and those who still come are tourists looking lost as they try to make their way through a maze of fencing to the jetty.

Bill Edgar of Golden Sun Cruises says his turnover has plunged from $840,000 in 2011-12 to $187,000 in 2014/15.

“Thanks, Barnett,” Mr Edgar told reporters.

Federal member for Perth Alannah MacTiernan said it was unfair that businesses starting up at Elizabeth Quay would be getting rent relief for up to two years but existing traders were missing out.

“When you’re not giving them the access to their premises that they signed up to, you need to ensure that they are compensated for that,” the Labor MP told reporters.

Ms MacTiernan said Elizabeth Quay would be a good development but it could take up to a decade to complete and some of the Barrack Square businesses wouldn’t last that long at their current rate of turnover loss.

“The GFC and collapse of mining have made things much more difficult. But it does mean that this project is probably going to take a lot longer to reach fulfillment than was projected.

“This makes the situation of these groups of tenants even worse.

“It is just completely and utterly unfair and uncommercial to be demanding that they pay virtually the same rent through this period.

“There needs to be proper compensation given to these people.”

An alliance of the businesses, the Barrack Street Jetty Traders, has written to their effective landlord, Premier Colin Barnett, asking him to intervene.

They wrote that Transport Minister Dean Nalder had promised after a meeting on June 10 to provide all traders with immediate rent relief for three months.

“This has not been the case,” they wrote.