A SHADOWY group of business leaders who funnelled more than £400,000 through the Democratic Unionist Party in Northern Ireland to support the Brexit campaign are prepared to bankroll opposition to Scottish independence if a second referendum is called.

The Constitutional Research Council (CRC) reportedly used a loophole in election laws to keep the donors' identities hidden. By channelling the money though the DUP – where because of perceived security threats in Northern Ireland donors can remain anonymous – they escaped having to declare contributions, as they would have had to do in Scotland, England and Wales.

The CRC is chaired by former vice-chairman of the Scottish Conservative Party Richard Cook. It has already said it would be willing to donate to a positive pro-union campaign in a second independence referendum.

DUP MP Sir Jeffrey Donaldson said: "It [CRC] has been involved in Scotland, for example supporting unionism in Scotland, and it approached the DUP to support our campaign during the referendum because it supports unionist causes in the United Kingdom."

The DUP has been under mounting pressure to reveal the name of the donor which enabled it to promote its Leave message on a UK-wide basis, including the purchase of a four-page Vote To Leave EU advert in the British Metro newspaper – a publication not circulated in Northern Ireland.

The leader of the cross-community Alliance Party, Naomi Long, said questions remained over the DUP's Brexit expenditure.

She said the party should release a detailed breakdown of how the money was spent. "Would the DUP have campaigned as vigorously for Brexit had they not received a large donation to do so?" she said.