The Kessock Bridge was one of three major crossing built in the past decades
Communities bypassed following the building of three bridges continue to suffer more than 20 years after the structures opened, it has been claimed.
Reay Clarke, who suggested bridging the Moray, Cromarty and Dornoch firths in the 1960s, said more had to be done to help towns and villages to recover.
The farmer and Highlands MSP Jamie Stone said central Sutherland was the area hardest hit.
The pair were interviewed for BBC Radio Scotland's No Going Back series.
Mr Clarke, of Edderton, said the eventual decision to build the three crossings has been proved right, but some of the communities that were bypassed by the bridges have never been properly compensated for the loss of the through traffic on the A9 road.
Meaning Parliament Field in old Norse, Dingwall was the administrative centre for a large part of the north of Scotland and the island of Lewis.
Dingwall's responsibility for Lewis ended in the 1970s when work on the Kessock Bridge also began.
Bonar Bridge was at one time a stopover on the journey between Inverness and the far north.
He said: "Dingwall lost its status.
"With the regionalisation of local government Dingwall lost the headquarters of Ross and Cromarty County Council which was a big blow to it and everything now has moved to Glen Urquhart Road in Inverness.
"One or two communities really have pulled through. Beauly seems to have a bit of a buzz about it.
"The two hit in a really bad way are Bonar Bridge and Ardgay. Shops have closed, people have moved out, there are no new houses being built.
"If you drive through you get a sense of deterioration and lack of growth."
Mr Clarke added: "Though they spent a huge amount of money on the bridges, very little was spent trying to help the bypassed communities."
Mr Stone said efforts had to be made to encourage tourism to the affected communities.