The peer led the SDP in the late 1980s as it carried out negotiations to merge with the Liberal Party.

Lord Maclennan then became joint interim leader of the merged party.

He served as an MP in the Highlands for 35 years, retiring from his Caithness, Sutherland and Easter Ross seat in 2001.

Acting Leader of the Liberal Democrats Sir Ed Davey said: "Bob was the kind of politician we all strive to be.

"Considerate, honest and hardworking with an uncanny ability to reach out across the political spectrum to find common ground.

"He was also a great servant, over many decades, to his Highland constituents. A passionate advocate of devolution, he campaigned tirelessly for the creation of the Scottish parliament and wider constitutional reform.

"As Liberal Democrats, we also pay him a huge debt of gratitude. It was his determined leadership and bravery that proved critical in the formation of the movement we know today."

Lord Maclennan, who was a Labour MP before joining the SDP, was parliamentary under-secretary at the Department of Prices and Consumer Protection in the late 1970s.

Scottish Liberal Democrat leader Willie Rennie said: "Bob was such a kind and generous gentleman who was passionate about social democracy and fairness.

"He was a dedicated servant for the Caithness and Sutherland and founder of the Liberal Democrats. A close friend and mentor to many in the party he will be missed so much."