BETTER Together may be investigated by the Crown Office after they failed to file a complete return of their referendum expenses with the Electoral Commission.

In their statement to press, the commission said: “Registered referendum campaigners were required to submit to the commission invoices over £200. The submitted return of the registered campaigner Better Together is missing some information making the return incomplete.

“For such matters relating to the Scottish Independence Referendum the Commission liaises with the Crown Office and Procurator Fiscal Service (COPFS) in Scotland.

“We are consulting with the COPFS in order for them to consider whether they will open an investigation into this matter. Depending on the response from the COPFS the commission will then consider whether to take any further action itself.”

In a statement, Better Together said: “The Electoral Commission have been provided with further information in regards to any queries and have been provided with the supporting evidence they require for Better Together’s referendum expenditure.

“Any items of expenditure (train bookings for example) for which invoices could not be sourced are supported by bank statements showing this expenditure to ensure transparency in our returns.

“The Electoral Commission are legally obliged to liaise with the Crown Office in this regard. There is no investigation under way.”

Around £6.7m was spent by campaigners in the referendum. The figures released by the Electoral Commission yesterday showed that Better Together spent a total of £1,422,602 and Yes Scotland spent £1,420,800.

A total of 42 registered parties and campaign organisations took part in the referendum campaign last year. Although the Electoral Commission had released details of the spending and donations for the majority of those groups in February, yesterday saw the release of the money spent and received by Better Together, the Yes Campaign, the SNP, Labour and the Conservatives.

Those campaign groups who spent more than £250,000 had to submit an audited return to the Electoral Commission. All invoices for more than £200 had to be submitted.

Outside Better Together and Yes, the SNP spent £1,298,567 and Labour and the Tories combined spent £1,088,673.

The political parties who had representatives in the Scottish parliament were also allowed to spend large amounts of money ahead of the referendum.

The SNP had a limit of £1,344,000; the Labour Party had a limit of £831,000 and the Conservative Party had a limit of £399,000.

None of the parties breached their limits.

Campaigners were also obliged to share details of their donations. The No campaign received £1.5m more than the Yes campaign.

The biggest donors were Harry Potter author JK Rowling, who donated £1m to Better Together, and Colin and Euromillion winnersChris Weir, who gave Yes £500,000 each.

Advertising and leaflet printing was the main campign cost.