Ferry fares to the Northern Isles will be cut by more than 40% on average from next year, the transport minister has announced.

Humza Yousaf said road equivalent tariff (RET) would be introduced on Pentland Firth routes from the first half of 2018, with a variant for Aberdeen to Kirkwall and Lerwick also coming in to force.

RET ensures fares on ferries are roughly in line with the cost of travelling the same distance on road.

Islanders have been campaigning for the scheme to be introduced for a number of years.

Transport Scotland estimates foot passenger fares will fall by an average of more than 40%, with car fares down more than 30% under the scheme.

Yousaf said: "During my first visit to the Northern Isles as transport minister I committed to ensuring we would reduce ferry fares as soon as practically possible.

"It was a clear manifesto commitment and I'm very pleased we are now in a position to announce when that pledge will be delivered.

"These significant fare cuts will be rolled out in the first half of 2018."

He added: "It is also our intention to include the commercial operators on the Pentland Firth in this scheme and we will work with them to put a suitable system in place to allow that to happen.

"This reduction in fares will make ferry travel to and from the Northern Isles even more attractive for islanders and tourists."

The announcement has been welcomed by Liberal Democrats, who represent both Orkney and Shetland in the Scottish Parliament.

Orkney MSP Liam McArthur said: "To his credit, during his short time as transport minister, Mr Yousaf has always accepted the need to reverse the unfairness in the SNP government's approach to ferry fares.

"This proposed cut to fares is long overdue but very welcome.

"It will be important to study the detail of the government's plans and it is essential that all routes across the Pentland Firth have a chance to benefit from the funding available."