The DUP's Metro advert

In the closing days of the referendum campaign last year, the DUP took out a series of four-page wraparound adverts in every edition of the Metro newspaper in Great Britain.

At the time, the News Letter and other media reported how unusual such an advertising campaign was given the vast expense involved – and the fact that Metro does not circulate in Northern Ireland.

A DUP spokesman told the News Letter at the time that the advert had been paid for by the party.

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When asked whether there had been a donation to the party which funded the advertising, the spokesman said that all parties receive donations, but that the party does not identify its donors.

“All parties receive donations and we are funding this from party funds,” he said.

Unlike the rest of the UK, donations to Northern Ireland’s political parties remain secret, and those who gave them remain anonymous.

Last week, the national media began to take an interest in the matter, with a lengthy piece on the Open Democracy website questioning whether donor secrecy laws in Northern Ireland meant that ‘dark money’ could be funnelled into politics on the UK mainland via donations to Northern Ireland parties.

The article highlighted that other national referendum advertising – such as Brexit placards in Glasgow which included Jeffrey Donaldson’s name in tiny print – had been funded via the DUP.

And the article said that the Electoral Commission had made clear that whatever sum the DUP spent on the campaign had been over £250,000.

The article highlighted that this was vastly more than the £90,000 which the DUP spent on last year’s Assembly election campaign.

Arlene Foster was asked about the donation during UTV’s leaders’ debate last Thursday night.

She said that the DUP had received a donation from “an organisation in England that wants to see the Union kept”.

Then, later that night on BBC programme The View, Mrs Foster declined to say how much the donation was, saying initially “I don’t have the figure here so I don’t know how much it was”.

Presenter Mark Carruthers put it to Mrs Foster that she must have “some idea how much it was”.

She replied: “No, I don’t.”

Mrs Foster then went on to deny that she was saying she had “no idea” what the sum was but stressed that it had been “properly accounted for” with the Electoral Commission.

Mr Carruthers then asked Mrs Foster how much the DUP as a whole spent during the Brexit campaign.

Mrs Foster said: “I have no idea how much was spent. That was last June, Mark, and you’re asking me to go back over Electoral Commission returns from last June...”

Less than three years ago, in May 2014, the then-DUP leader Peter Robinson told the News Letter that his party would be prepared to voluntarily publish any future donations greater than £7,500.

He had said then: “It is our view that we would be prepared to – even though by law we are not required to – if we had any donations beyond the figure set by the House of Commons, then we would be prepared to have that publicised.