THE SNP is being investigated by watchdogs over a £1m election loan.

Tom Gordon

Scottish Political Editor

THE SNP is being investigated by watchdogs over a £1m election loan.

The Electoral Commission has launched a probe into the cash, which came from the party's biggest donors, the lottery winners Chris and Colin Weir.

The Ayrshire couple, who scooped £161m on the Euromillions draw in 2011, each made an interest-free loan of £500,000 on March 24 to help the SNP through the general election.

The Weirs also donated £500,000 each to the party on the same day.

All the monies should have been declared to the Commission by the end of April.

However, although the £1m in donations was duly recorded, the £1m in loans was not.

The borrowing, due to be repaid on July 31, was not officially registered until May 28.

The SNP last night blamed a technical fault at the Commission.

However the Commission said it was investigating a "failure" on the SNP's part.

In a statement, the Commission said: "The SNP failed to deliver its quarterly 'transaction' (loan) report to us by the required deadline of 30 April 2015. The Commission has commenced an investigation and is currently considering what, if any, action is appropriate in relation to SNP's failure to deliver its quarterly transaction return within the required timescale."

Under electoral law, a party treasurer can be fined up to £5000 upon conviction if they fail to file a transaction report on time without reasonable excuse.

The SNP treasurer is Colin Beattie, the MSP for Midlothian North and Musselburgh.

In 2013, he and his wife Lisa were censured by Scotland's standards watchdogs for failing to register a string of properties they owned while both were Midlothian councillors.

A Labour source said: "It's a bit embarrassing for the SNP that the multi-millionaires who bankroll their party have been dragged into an investigation like this."

An SNP spokesman said: "There was a technical issue with the online system for submitting reports, which meant that although the data was in the possession of the Electoral Commission on time, it was not in the correct form.

"This was rectified as soon as it came to light. We have previously raised concerns with the Electoral Commission about online and continue to discuss the matter with them."

The Weirs are the SNP's main funders, jointly donating £4m since September 2011.

The couple also gave £3.5m to the Yes Scotland campaign in the referendum.