At present the route runs from Stranraer, but stops more than a mile from Cairnryan, forcing cyclists to use the busy A77 trunk road.
The ‘missing link’ in cycling infrastructure was supposed to be completed as part of a planned A77 Trunk Road Improvement Scheme between Drummuckloch and Innermessan.
However, a Transport Scotland review in 2012 led to the scheme being ditched and excluded from the Scottish Government’s Motorway And Trunk Road Programme published in July 2013.
Speaking in a debate in the Scottish Parliament on active travel last week, Mr Smyth claimed it is yet another example of failure to invest in the south west.
He said: “We are again drawn to the lack of investment in infrastructure in the south-west.
“That includes active travel. For someone who arrives at Cairnryan by ferry with their cycle, their route to the nearest town, Stranraer, is along the A77 trunk road, together with 40-tonne lorries coming off the ferry.
“The utter failure of the Government to extend the national cycle route to Scotland’s largest ferry terminal presents a danger for people who want to cycle when they arrive in Scotland. Welcome to active travel Scotland.
“Let us all get behind the need to grow our investment in active travel to at least 10 per cent of the transport budget, but let us also unite behind ending the cuts to local councils and to rail and bus services and ensuring we have an equitable share of infrastructure investment in active travel for every community, including the most deprived and rural.”
In his closing statement The Minister for Zero Carbon Buildings, Active Travel and Tenants' Rights, Patrick Harvie, made no reference to anything Mr Smyth had said.
Speaking after the debate, Mr Smyth added: “Once again we see an example of a lack of investment in the south west, we really are the forgotten region of Scotland where national governments are concerned.
"It is simply not good enough and I will continue to fight for decent investment in infrastructure in our region.”