It has emerged two Highland villages where he wants to implement the scheme do not have filling stations.
Achnasheen in Wester Ross and Strathpeffer, near Dingwall, are among 10 rural communities in mainland Scotland and England earmarked for the Treasury's mooted 5p-a-litre cut in fuel duty.
But Achnasheen's pumps ran dry five years ago and motorists have to travel 10 miles to Kinlochewe to fill up. Residents of Strathpeffer must head to nearby Dingwall to replenish their vehicles with petrol or diesel.
Mr Alexander, the Liberal Democrat MP for Inverness, Nairn, Badenoch and Strathspey, said: "There are filling stations within the postcode area, otherwise it wouldn't be on the list."
Meanwhile, Mr Alexander has dismissed accusations of "pork barrel" politics by Labour who pointed out that eight of the 10 areas in the UK that could benefit from the duty cut are in areas held by the LibDem politician's party.