It follows delays to the repair of MV Loch Seaforth, which has been out of action for six weeks.
The ferry will not return to service on the Ullapool-Stornoway route until at least Monday – after that resumption date was put back three times.
This has had a knock on effect on sailings to Barra, Islay, Campbeltown, Skye and South Uist as vessels are moved around the network to plug the gap.
Mr Dey said: "I entirely recognise the intolerable nature of the situation for islanders on an individual and economic basis.
“We very much recognise the community’s frustration at the current disruption and the impact it’s having.
"We are doing everything we can supporting CalMac to maximise available capacity across the network.
"We are currently actively exploring options for chartering additional tonnage, including consideration of the suitability of the [Caithness-Orkney catamaran] MV Pentalina to increase resilience across the network.”
Western Isles SNP MSP Alasdair Allan said he had been “deluged by emails from families desperate to visit relatives on the mainland who have had long-booked tickets cancelled, businesses who can no longer get building materials to the islands or export shellfish, and tourist businesses struggling to cope with the news that all bookings are suspended for a fortnight."
He said the six-year-old Loch Seaforth “should not be experiencing technical issues of this severity”.
The vessel has been out of action since mid-April and was initially expected to be back in service on May 17, but this was later revised to May 21 and again to May 28, and now to May 31.
CalMac said the ferry was now due to leave Greenock on Friday following the completion of repairs and successful testing.
It would undergo the required 50 hours of sea trials en route to Stornoway before resuming sailings on Monday.
The operator said after initial engine repairs, damage to the crankshaft was found and a bearing had now been replaced.
It said if the ferry returned to service on Monday, the Barra-Oban, Lochboisdale-Mallaig and Mallaig-Armadale services would resume on Wednesday, when the Islay-Kennacraig route would return to a two-vessel service.
CalMac said a two-ferry service would restart on the Brodick-Ardrossan the following day and Campbeltown sailings would start, which has been delayed from April 29.
Managing director Robbie Drummond admitted it had been an “extremely frustrating time for passengers and our staff”.
An industry source claimed to The Scotsman that the engine part which had failed – a piston crown or head - had exceeded the manufacturers’ recommended operating hours but was not replaced during the vessel’s last maintenance period.
However, CalMac said the cause of the engine breakdown was still being investigated and its findings were still awaited.
Mr Drummond told The Scotsman: “The specialist contractor is investigating why it failed.
"This is a complex process and we have not yet had the technical reports from the contractor to confirm the root cause.
"Anything else being discussed just now is speculation.”