The Transport Minister has denied that he misled parliament over the tendering of a ferry contract which has resulted in strikes.
Keith Brown previously said he had "no idea" whether publicly owned operator CalMac lodged a cheaper bid to run the Northern Isles ferry service than successful private-sector bidder Serco NorthLink when he awarded the contract.
Labour infrastructure spokesman Richard Baker challenged this claim, insisting that the CalMac bid reached an advanced stage and was fit to be considered.
Transport union RMT is running five 24-hour strikes from Friday until December 30 against Serco's plan to reduce staffing levels.
Mr Brown made a statement on the dispute to Holyrood, urging both parties to find a resolution to avoid disruption over the festive period.
Labour accused Serco of being involved in tax avoidance and having a "poor industrial relations record", while the Conservatives criticised the RMT for "punishing families and businesses in Orkney and Shetland at this festive time of year".
Mr Baker said: "Why did the minister say he was unaware of the value of CalMac bid because it couldn't be considered, when we now know from a freedom of information request that the bid had indeed reached the final round of scoring? Is it not now time for a full investigation into the process, which I've asked the ombudsman to look into, a process described by the RMT as a botched privatisation stitch-up?"
Mr Brown said Mr Baker's statements "belong in the realms of fantasy". He said: "The accusation about misleading parliament is a very serious one. I stand by fully the statement I made previously to parliament that I did not see the price of that bid because it did not reach the final stage in terms of satisfying the previous criteria."
The Northern Isles routes "have been operating at staffing levels that are higher than required for a large percentage of the year" and a number of bidders for the route indicated their intention to reduce staffing levels, Mr Brown said.
There have been no compulsory redundancies and remaining staff have been offered "favourable terms and conditions" and an inflation-busting 4.25% pay rise, according to Mr Brown.