Cruise ships could be deterred from stopping in Scotland due to changes to the system of immigration checks for passengers, an industry body fears.
The UK Border Force previously cleared cruise ships in advance, on the basis of passenger and crew manifests.
But now passengers must have documents checked, face to face, at the first UK port of call.
Although the rules have not changed, the UK Border Force is said to have changed its interpretation of them, the BBC reported.
Cruise Scotland, which promotes Scottish ports as a destination, warned the changes could damage the industry.
Cruise ships are said to have brought 379,955 people to Scotland last year, up 19% on 2011, and the industry is estimated to contribute £41.2 million to the Scottish economy.
Cruise Scotland chairman Richard Alexander said there was “dissatisfaction” within the industry over the changes.
“At a time when cruise lines are already facing increasing operational costs, this is effectively a new tax on their operations,” he said.
“They have also indicated that this will make the UK uncompetitive and unappealing and act as a deterrent for ships to call at UK ports.”
SNP MSP Stuart Macmillan, convener of Holyrood’s cross-party group on recreational boating and marine tourism, has contacted UK immigration minister Mark Harper for clarity on how the rules will affect Scotland.
Macmillan said: “I have heard passengers have faced lengthy delays as a result of this system which is having a detrimental effect on the industry in Scotland.
“Serious concerns have been raised about the UK government’s immigration checks for cruise ship passengers that cannot be ignored.
“I have written to Mr Harper to ask for clarity on how these rules are affecting Scotland as the voices from the industry say it is hugely negative and must be changed before it is too late.”
A Border Force spokesman said: “There have been no changes to immigration rules affecting cruise ships. We conduct full checks on all cruise passengers entering the UK to ensure our borders are not compromised.
“We welcome genuine visitors to the UK and we are in discussions with Cruise Scotland to make sure effective plans are in place to protect the border with the minimum inconvenience to passengers.”