It will pass 15m below the canal and is described by engineers as a challenging but feasible project.

As a result the Inverness authority will have to persuade the Scottish government to hand over £118m to pay for Inverness's southern bypass, £35m of which is the increased cost of the tunnel.

The decision will make canal passages quicker as bridge opening will no longer be constrained by rush-hour traffic.

'The crossing of the Caledonian Canal and River Ness is clearly a hugely important decision and our preferred option was always to avoid any more moving bridges,' said British Waterways.