BUSINESS leaders who have pledged to fund a defence of the union in any future independence referendum are warning about the dangers of running another Project Fear: the Refrightening campaign.

Richard Cook, the chairman of the Constitutional Research Council (CRC) and a former vice chairman of the Scottish Conservatives, has told how the “prudent and responsible thing to do is to plan” for a re-run of the September 2014 vote.

Yesterday’s Herald revealed how the CRC – which includes several unnamed Scottish business leaders – were the mystery donors behind a £400,000 Brexit fund handed to Northern Ireland’s Democratic Unionist Party.

Despite mounting pressure, the DUP leader Arlene Foster had always refused to identify the donors.

The money paid for a controversial £282,000 advert in the Metro newspaper just days before Brexit vote, even though the paper is not circulated in Northern Ireland.

Today, Mr Cook said that by mounting a campaign to save the union his group could be accused of acknowledging that “a second IndyRef is inevitable.

But he called for Unionists to “learn the lessons of the past” and plan for a “better Better Together”.

He said that the real lesson of the 2014 campaign was “campaign for the Union, not against independence”, adding: “The last thing we want our side to be is Project Fear: the Refrightening.

He also reiterates his view that “Brexit would be good for the Union, and correspondingly bad for nationalism”, despite Nicola Sturgeon putting another vote “on the table” in the wake of the result.

He adds: “The end of amateurism is now: the Union deserves nothing less than our best effort.”

CRC sources estimate that they bankrolled 95 per cent of the DUP’s £425,000 Brexit campaign spend.

But its initial target, the official Vote Leave campaign, had reached its donation cap and could not accept any more cash, so they gave to the DUP instead.

Because of the Troubles, the names of donors to political parties in Northern Ireland are kept confidential amid claims they could face reprisals if they were identified.

CRC sources said that those who had given to the Brexit fund did not want to be identified because of concerns about being seen to give money to a Northern Irish party.

They said all were British Nationals able to vote in UK elections and compliant with criteria set out by the elections watchdog, the Electoral Commission. But Sinn Fein’s Conor Murphy said that the donation “made a mockery” of the DUP’s own calls for transparency in politics before next week’s Stormont Assembly elections. “It is still not clear who is in the group .. and what the group got in return for this huge donation,” he said.The leader of the cross-community Alliance Party, Naomi Long, also called for full transparency. “so that people can make their own judgment as to whether parties are acting on their behalf as the electorate or on behalf of those with deep pockets and fat wallets.”

The SNP, meanwhile, accused the group of harming Scotland by backing Brexit.

SNP MSP James Dornan said: “Any future anti-independence campaign will be tainted by being bankrolled by a group who deliberately undermined Scotland’s interests and long-term economic wellbeing to defend the Union at all costs.”