The author of a study that estimates rising ferry fares have seriously damaged the provincial economy is standing by his conclusions in the face of sharp criticism from Transportation Minister Todd Stone.

Peter Larose 31 million more passengers would have taken BC Ferries over the last 10 years had the province kept fare hikes to the rate of inflation.

He pegged the losses at $2.3 billion in economic activity and $610 million in taxes to various levels of government.

"I have extreme confidence in the results," Larose said, adding they are more likely an underestimate. "I think it's probably significantly higher."

He spoke to a policy session at the Union of B.C. Municipalities convention in Whistler Tuesday after Stone issued and took to the airwaves to condemn the .

"It is unfortunate that the analysis speculates on what might have been, rather than providing any concrete solutions on how to take the coastal ferry system into the future in a cost effective and sustainable way," Stone said in a Sept. 19 letter to UBCM's president.

The minister said the study failed to properly consider various factors, from the effects of the 2008-09 global recession to rising fuel prices and demographic changes.

He said it was "irresponsible" and "unproductive" for UBCM to release the "unsubstantiated and sensational" estimates.

Stone's letter also said the analysis was flawed because it assumed all the money not spent due to reduced ferry travel went out of the province, instead of being spent in B.C. in other ways.

Larose sought to reassure UBCM delegates that his projection is correct and doesn't mean the economic damage in coastal B.C. is being offset by gains in other parts of the province.

But Tofino Coun. Ray Thorogood questioned that logic, arguing Lower Mainland residents deterred from a trip to Vancouver Island by high fares might instead head east to the Okanagan.

"We're not saying this is the be all and end all of all analysis," said Campbell River Coun. Claire Moglove, who sits on the UBCM committee that commissioned the work.

She said the aim is to do further work and engage the province in a real dialogue on stemming the decline in BC Ferries ridership.

"What we want from the provincial government is to sit down and start talking about solutions."

Moglove added that UBCM decided to probe the impact of high fares because the province wouldn't.

UBCM delegates vote Wednesday on a resolution in response to the findings.

Current rate caps allow for maximum increases of four per cent this year and 3.9 per cent in 2015.