Banff and Buchan MP Dr Eilidh Whiteford is backing calls for Royal Mail to deliver a freeze on the price of stamps.
Stamps have increased in price closely in line with inflation over the past 30 years but have increased in 2012.
Following the privatisation of Royal Mail, there are fears that the price of stamps will continue to rise.
The SNP’s Postal Affairs spokesperson Mike Weir has called for Royal Mail to freeze the price of a stamp and give assurances that the sell-off will not lead to further price hikes.
The SNP has said Westminster’s approach to the Royal Mail contrasts with that of the Isle of Man, where the post office remains in public hands and it is cheaper to send a letter from the island to anywhere on the UK mainland than it is to send one between Scotland and England.
Commenting, Eilidh Whiteford said: “Our postal services are far too important to simply be sold off on the cheap in the way Westminster has done.
“What we now need from the privatised service is an assurance that the price of a letter will not increase before Scotland becomes independent.
“It is cheaper to send a letter through the Isle of Man’s publicly owned postal service to the mainland than it is to send one from Scotland to England – and the fear must be that privatisation will only make this worse.
“It is clear that the only way for Scotland to have the postal service it wants and deserves is with a Yes vote next year.
“The SNP have pledged to act to maintain a universal six-day a week postal service in an independent Scotland and bring the Royal Mail back into public ownership where it belongs.”