Renewed concerns over freight capacity are being raised, with a report recommending action as soon as possible.
It comes after new figures showed urgent and immediate need for an additional freight vessel.
A study has claimed six in 10 northbound and four in 10 southbound sailings are running at at least 90 per cent capacity, with one in 10 over the allotted capacity.
Shetland’s Stewart Building Transport Group has met Scottish government transport minister Jenny Gilruth to present the findings.
Concerns over freight capacity have been raised by the transport group for several years.
The growing need is seen as all the more pressing given the thriving Shetland economy.
The study, conducted by AB Associates and SSQC, recommends an additional freight vessel be chartered from now until the time when new freight vessels are introduced on the North Isles route.
Stewart Building Transport Group chairman, Tavish Scott, said: “We know that, in freight terms, the Aberdeen-Lerwick-Aberdeen route is the highest earning route in the Scottish island ferry network, generating in excess of £10 million per year, the profits from which are fed back into the public purse.
“Despite this, it is often running at or over capacity and simply not meeting industry needs, which in turn impacts on the island’s economy and that of Scotland as a whole.
“The report clearly demonstrates that the service has not only reached capacity, there is absolutely no room for growth or, indeed, anywhere near adequate provision to handle peak periods or potential disruptions to service.
“We were encouraged by the minister’s engagement and are delighted that she has accepted a formal invitation to visit Shetland to get a real, first-hand understanding of the challenges experienced by industry, hauliers and the service provider.”
The study looked at current freight, volumes, projected volumes for 2022, and weekly freight patterns, relating to shared services with Orkney.