The SNP is being investigated by Scottish Parliament authorities over the potential misuse of postage stamps bought using MSPs’ expenses.

In an email, seen by the BBC, an individual claims that stamps bought on expenses were passed to UK election candidates for campaigning activities, such as sending letters to voters.

The anonymous complaint was submitted to Holyrood’s presiding officer Alison Johnstone.

The Scottish Parliament said it was investigating the matter to establish whether there had been any misuse of parliamentary resources.

BBC Scotland News has also seen a screenshot from a WhatsApp group, made up of staff who work for SNP MSPs, where there is a discussion about whether or not the stamps can be traced back to the purchaser.

MSPs are allowed to spend up to £5,500 a year on postage and stationery as part of parliamentary resources provided by the Scottish Parliamentary Corporate Body

The Scottish parliament’s rules state that they “must be used only for parliamentary duties and must not be used for any other purpose, including party political purposes”.

The UK Electoral Commission also sets limits on how much political parties and candidates are allowed to spend during campaigns.

The SNP Holyrood Group said parliamentary rules were “crystal clear”.

A spokesperson said: “These exchanges, whilst obviously light-hearted, are being investigated as is appropriate and we would expect the offices of MSPs of all parties to cooperate with the Parliamentary Corporate Body.

“Materials, including stamps, can only be used for parliamentary purposes such as representing constituents and campaigning on their behalf.

A Scottish Parliament spokesperson said: “We take the use of publicly funded resources very seriously.

“Officials are investigating the matter to establish whether there has been any mis-use of parliamentary resources.”