It follows lorries being excluded from the Scottish Government’s road equivalent tariff scheme (RET), which cut fares by up to 40 per cent, after a three-year trial which ended last April.
A consultants’ report for the Scottish Government’s Transport Scotland agency which was published today found the move had had a “significant negative impact” on hauliers.
Labour transport spokeswoman Elaine Murray said: “A report commissioned by [transport minister] Keith Brown himself provides evidence that his decision to remove RET from commercial vehicles has been a disaster.
“He must now come to Parliament and explain what he will do in light of the report.”
Comhairle nan Eilean Siar - Western Isles Council - said the study confirmed the move had hit the islands’ economy and showed that hauliers did pass on the savings they made from RET to consumers, and since the removal of RET prices had increased.
Council leader Angus Campbell said: “The findings of this independent study are absolutely unequivocable. The Scottish Government now has the evidence that RET was working as planned and there were real, substantial benefits to the fragile economies of island areas.
“The removal of RET for commercial vehicles has been damaging for the economies of the islands, particularly smaller islands such as Barra, Benbecula and the Uists, and has been detrimental for consumers who have faced increased prices as a result.
!I call on the Scottish Government, as a matter of urgency, to take the sensible course of action and reinstate RET in full, including for commercial vehicles.“
The Outer Hebrides Commerce Group Co-ordinator Gail Robertson said: “We are pleased that after months of delay the transport minister has finally published this study.
“It is an instructive document that clearly shows the devastating, negative impact the removal of cheaper fares are having on island families and businesses.
“We can appreciate why Keith Brown was reluctant to publish this document - it nails and dispels many assertions that were untrue.”
The Scottish Government said it was forming a working group to review of commercial vehicle fares across Scotland’s ferry network.
Its spokesman said: “Our aim is to deliver a commercial vehicle fares structure for all Scotland’s islands that is fair, transparent and straightforward as well as delivering best value for taxpayers at a time of severe cuts to the Scottish Government budget.
However, he said the report stated it was hard to assess the impact of the removal of RET against the general economic slowdown, with a 16 per cent increase in haulage costs between 2008 and 2012, mainly due to fuel price rises.
The spokesman said: “We want to see ferry fares that support island communities and are investing an additional £2.5 million to support hauliers to the Western Isles, Coll and Tiree where fare increases have also been capped, and we have ensured commercial vans benefit from the same fares as ordinary motorists.
“We have invested an estimated £500,000 a year to provide RET to Islay, Colonsay and Gigha from October 2012.
“We will be investing more in RET as we roll it out to all Clyde and Hebrides islands in the lifetime of this Parliament.
“We have also put in place additional support for the agricultural and aquaculture industries in response to their requests.”