THEY are the lifeline ‘boats’ which link Orkney and Shetland to the rest of Scotland.

The Hamnavoe, Hrossey and Hjaltland are owned and subsidised - ultimately - by the Scottish Government. But they are operated by one of the UK’s biggest private outsourcing firms, Serco.

Next month SNP ministers will have to decide whether to let Serco keep a contract to run Northlink Ferries or hand the service over to nationalised giant Calmac. At stake is more than £600m over the next eight years - and the party’s perceived commitment to public ownership.

Trade union RMT - already in dispute with Serco over its management of the Caledonian Sleeper train - has launched a bitter attack on what it called SNP’s “unhealthy relationship” with the company, a claim which has angered government insiders.

The union, one of few to support a Yes vote in the 2014 referendum, has long been demanding that the in ferry argot - be fully nationalised.

But its most recent attack came after a Serco subsidiary involved in electronic tagging of offenders was fined £22.9m in fines and costs after a six-year investigation in to fraud and false accounting by the Serious Fraud Office. Serco has admitted to problems at the subsidiary and the SFO has welcomed steps it has taken to prevent their repetition.

However, RMT General Secretary Mick Cash said: “Once again, Serco, the specialists in failure, have been found out. Fraud and false accounting are serious offences that should make any Government think twice about using private companies to deliver essential public services.

READ MORE: Critics call for ferry overhaul following latest CalMac breakdown 

“Yet Serco continue their incompetent handling of new rolling stock on the Caledonian Sleeper contract at RMT members and passengers expense without the prospect of any censure from the Scottish Government.

“And on lifeline ferries, Serco have never been required to state the profits they take out of Northern Isles Ferry Services contract they were awarded by the Scottish Government in 2012.

“Despite this, Serco could be awarded the next NIFS contract in August, when MSPs are on holiday.

“Workers, passengers and communities, especially in Orkney and Shetland, deserve the stability and certainty of a publicly operated and run ferry service, not another gamble on Serco Group’s predatory empire.

Serco earlier this month accepted the fine. Its chief executive, Nicholas Soames, said: “Those of us who now run the business are mortified, embarrassed and angry that, in a period between six and nine years ago, Serco understated the level of profitability of its Electronic Monitoring contract in its reports to the Ministry of Justice. Serco apologised unreservedly at the time, and we do so again.”

The company has been at loggerheads with RMT for some time with the union currently angrily denouncing its handling of their dispute on the Caledonian Sleeper. RMT members are currently balloting for industrial action.

Serco and SNP-run Glasgow council have also had a challenging relationship over the way the outsourcing firm handled the eviction of former asylum seekers it housed in the city.

READ MORE: CalMac hits out at council after ferry in ‘near-miss’at ‘too dark’ pier 

SNP ministers and officials at the Scottish Government and its quango Transport Scotland cannot say very much about the current tender. They are due to make a decision in August over who runs the three Northlink boats from October of this year. There are only two potential candidates, Serco and CalMac, which operates Clyde and Hebridean ferries. A private ferry operator, however, is challenging the whole process on “state aid” grounds.

The Scottish Government said RMT rhetoric on the Serco’s tagging controversy had nothing to do with ferries to Orkney and Shetland.

A spokesman said: “These fines are completely unrelated to Serco’s contracts with the Scottish Government and attempts to connect them are misleading at best. Any bids submitted to the Scottish Government must follow robust procurement rules and be compliant with the financial requirements specified in the Invitation to Tender.”

Serco tried and failed to take CalMac’s west coast contract recently but robustly defended its performance on the northern routes.

Stuart Garrett, Serco’s Managing Director at NorthLink Ferries, said “Our track record of customer satisfaction, reliability, safety, community support and continuous improvement speaks for itself. Since taking over the service, we’ve increased passenger numbers by 10%, vehicles by 28%, and freight volumes by 11%. Thanks to our team, including the vast majority of local staff we employ, our reliability performance is 99.97%, underlining how committed we are to keeping the islands connected with our lifeline services.”

RMT represents many Northlink Ferries workers and has been campaigning for nationalistation for some time. A parliamentary motion backing a state operator won cross-party support before Holyrood broke up for the summer. A tender announcement will probably be made before politicians reconvene in September.

The quality of ferry services is likely to be one of the issues at the front of voters minds in the Shetland by-election, also scheduled for next month.

The frontrunner to replace retiring MSP Tavish Scott - a former transport minister - is Liberal Democrat candidate Beatrice Wishart.

She said: “People in Shetland want an operator that can deliver reliable services.

“The big challenge is getting an efficient operator in place.

“The government needs to be completely transparent about the tendering process going forward.”

Scottish Labour by-election candidate Johan Adamson said: “The service currently provided by Serco Northlink is just not fit for purpose.

“In order to be able to afford to travel, people often have to undertake the overnight journey without a bed.

“Otherwise families are facing an outrageous bill of up to £500 for a return trip to Aberdeen, including the cost of travel with a car.

“Lifeline services should be provided for the public good and that’s why Scottish Labour would bring these contracts in house, ensuring that profit is put back into the community