A Scottish transport group is set to benefit from the boom in oil and gas investment in Shetland this year after enjoying a surge in profits helped by public sector investment in Orkney.

Streamline Shipping Group's experience provides further evidence of how record levels of investment by oil and gas firms are helping fuel growth in other sectors across Scotland.

Managing director Gareth Crichton said the group will enjoy a boost to turnover after capitalising on oil and gas firms' moves to develop fields west of Shetland.

He said the group has recorded a big increase in demand for the shipping services it provides between the mainland and Shetland in connection with the new gas terminal that is being built next to BP's giant plant at Sullom Voe. This will handle output from the Laggan and Tormore fields that Total is bringing onstream.

Streamline runs a container service that links Aberdeen with Orkney and Shetland.

Mr Crichton said Streamline has been employed to charter ships to bring a range of specialised parts from places such as northern Italy for use in the terminal.

Oil and gas industry work has also led to a big increase in demand for Streamline's haulage services to transport goods around the Shetland islands.

The increase in business puts the company on course for another good year. It grew pre-tax profits to £613,000 in the year to December from £70,000 in the preceding period. Turnover increased to £26m from £21.5m.

Mr Crichton said Shetland oil and gas traffic helped trading in the second half. However, much of the growth was driven by public sector construction activity in Orkney. Work on building new schools at Stromess and Kirkwall and a leisure centre in the town led to a spike in demand for shipping services from construction firms such as Morrison.

"We worked with a number of contractors," said Mr Crichton, who noted the company specialises in moving heavy equipment. We had a good shift."

However, Mr Crichton highlighted concerns about the long term outlook for container services to Shetland and Orkney.

These are subsidised under a contract with the Scottish Government that ends in 2014.

He also emphasised the company's unhappiness with the Scottish Government's decision to award a £243m contract to run lifeline ferry services to the Northern Isles to Serco group rather than Streamline.

The group is seeking damages from the Scottish Government in the Court of Session over the decision, following what it claims was a flawed procurement process.

A Transport Scotland spokesperson noted that in a judgement issued in May last year Lord Malcolm did not accept Streamline's accusation that the department's approach to the tender of the Northern Isles ferry service tender had lacked transparency.

He added: "We are surprised that the company continues to take this line and will continue to robustly defend our actions in the award of this contract."

Mr Crichton said efforts to diversify the group and boost margins have been paying off.

The group has started providing services linking Scotland with Norway, Russia and Holland with an Icelandic company.

The Lincs Forwarding freight business, the company bought in 2011, has moved into profit.

The group provides a range of port related services in Aberdeen, Orkney and Shetland.

It also offers haulage and storage services from depots across the country, including one in Bellshill, Lanarkshire.