First Minister Alex Salmond has been referred to the standards watchdog regarding a meeting with SNP donors at his official residence just days before they handed £1 million to the party.
Mr Salmond hosted Euromillions winners Chris and Colin Weir for tea at Bute House in September shortly after they scooped the £161 million jackpot.
The visit was not officially recorded and no minutes were taken.
Mr Weir is a former SNP candidate and long-time supporter of Scottish independence.
Labour parliamentary business manager Paul Martin believes Mr Salmond breached rules relating to separation of ministerial and constituency roles, the use of public resources for party political purposes and a duty to record formal meetings.
The code also states: “Government property should not generally be used for constituency work or party activities. A particular exception is recognised where a building has been designated as the First Minister’s official residence.
“Where ministers host party or personal events in the First Minister’s official residence, it should be at their own or at party expense, with no cost falling on the public purse.”
Mr Martin has written to Dame Elish Angiolini, independent adviser on the Scottish ministerial code, to investigate his complaints.
He said: “It is not befitting of someone holding the office of First Minister to chase after lottery winners and hold tea parties for them at his official residence in a bid to secure donors for his separation campaign.
“This is a party which auctioned off lunches with the First Minister in the Scottish Parliament to raise campaign funds and changed its policy on bus regulation at the first sign of a cheque from Brian Souter.
“It is hypocritical of the First Minister to attack David Cameron for abusing his office for party purposes, yet does not see anything wrong when he does the same.”
Former lord advocates Dame Elish and Lord Peter Fraser were appointed independent advisers to the ministerial code in August and consider complaints made under it.
The pair replaced Lord David Steel and George Reid who considered three complaints against the First Minister during their three year tenure, all of which were dismissed.