A lavish campaign dinner for the Scottish party is being co-ordinated by the "United and Cecil Club" (U&CC), a body that had to forfeit an illegal donation last year.
SNP Westminster leader Angus Robertson said the revelation raised questions about how the Conservatives planned to fund their referendum strategy. Scottish Tory chief Ruth Davidson last month kickstarted her bid to stop independence by launching a new group, "Conservative Friends of the Union".
To this end, new treasurer James Stewart sent a letter to Tory supporters about a dinner in the Signet Library in Edinburgh in June.
The event, hosted by hereditary peer Lord Strathclyde and attended by Surrey Heath MP Michael Gove, will raise cash "to fight Alex Salmond's separatist agenda". According to the letter, a table of 10 for this "memorable evening" will cost £1,500.
Stewart, who helped bankroll Davidson's leadership campaign, stated: "I am very excited about repositioning the Scottish Conservatives under Ruth Davidson's dynamic leadership and beginning the process of seizing the initiative from the Scottish Nationalists."
However, the letter makes clear the pro-Scotland dinner is being organised in the southeast of England.
The administration of ticket and table sales is being "co-ordinated" by the U&CC, a Tory dining club formed from a merger of different organisations in 1949. The address of the club is given as "Hickmans Lane, Lindfield, Haywards Heath". The Sussex town is over 350 miles from Scotland, while the address given in the letter is a three-bedroom detached house.
The U&CC has around 400 members and holds events to raise party funds. According to the Electoral Commission, the organisation has donated £100,000 to the party since 2008. None of the registered donations went to Scotland.
In November, the U&CC had to forfeit an "impermissible" £850 from a donor who was not on the UK electoral register and could not make a legal donation.
Relying on a body in Sussex is the latest financial blow for the Scottish Tories. The party's legendary fundraiser, Sir Jack Harvie, retired from the role weeks after Davidson became leader. Contributions from donors Malcolm Scott and John McGlynn have dried up.
One senior Tory source said the U&CC link reflected badly on Stewart: "The new treasurer has made the Scottish party a laughing stock. The SNP will ridicule us for this, and it will confirm to the other Unionist parties that we are simply a handicap that should neither be seen nor heard in the referendum campaign.
"Any treasurer worth his salt should be able to organise fundraising dinners in Scotland, by Scots, and for Scots."
Robertson, also the SNP's referendum campaign director, said: "Involving the United and Cecil Club, which was found to have received an illegal donation, again raises questions over how the Tories intend to bankroll the anti-independence campaign."
A Scottish Tory spokesman said: "The Scottish Conservative Party has a number of fundraising events each year. All donations received are fully declared through the Electoral Commission."