A former Scottish Tory candidate linked to a controversial “dark money” donation during the Brexit referendum could be asked to appear in front of MPs.

Richard Cook, chair of the secretive Constitutional Research Council, which famously gave £435,000 to the Democratic Unionist Party during the campaign, has been contacted about the CRC by a powerful Westminster committee.

A spokeswoman for the Digital, Culture, Media and Sport (DCMS) committee said they had received “nothing in response” from Cook, adding that one of the options available was to call him to give evidence in person.

However, a spokesman for Cook said: “Richard replied five days in advance of the deadline. DCMS lost the letter.”

The row came as the Prime Minister's EU withdrawal plan came under further attack at the DUP conference yesterday.

The Leave side secured victory in the EU referendum, but the funding of a number of pro-Brexit groups has been under the spotlight since the result.

In particular, businessman Arron Banks has come under pressure over the millions of pounds he gave to an unofficial Brexit campaign, leave.eu.

Another controversy erupted after it emerged that the little-known CRC had provided Northern Ireland’s pro-Brexit DUP with £435,000 during the campaign.

Around £425,000 of the sum was spent on an advert in the Metro newspaper, which is not sold in Northern Ireland.

The DUP did not have to reveal that the CRC was the source due to donor secrecy laws, but the body’s identity was declared voluntarily.

Since then the CRC has faced questions about where it got the so-called “dark money” donation from, but few details have come to light.

Cook, a former senior office bearer in the Scottish Tories who lives in East Renfrewshire, chairs the CRC, which was founded around four years ago.

In an interview last year with the Sunday Herald, he said: “The CRC is regulated by the Electoral Commission. We operate solely in the UK. We accept donations only from eligible UK donors. We donate solely to permissible UK entities.”

However, he declined to offer any information on the identities of CRC donors and members: “I’m not going to get into the donors, like I am not going to get into the members.”

Asked how much money had been donated to the CRC since 2014, he said at the time: “I’m not going to get into that.”

On whether it was over £1m, he replied: “Not going to get into that.”

Cook attended the UK Conservative conference after the Brexit referendum and Scottish Tory leader Ruth Davidson recently confirmed he is still a party member.

It can now be revealed that Westminster’s DCMS committee has written to Cook about the CRC. The Committee has a high-profile inquiry into “disinformation and ‘fake news’” and part of the probe has included a focus on issues relating to the pro-Leave side.

However, there was confusion last night over the contact between the committee and Cook.

After this newspaper informed the committee that Cook’s spokesman had said that “Richard replied five days in advance of the deadline”, a committee spokeswoman said yesterday:

“I have just confirmed with the Clerk of the Committee that we have received nothing in response from Richard Cook. The letter to him refers to the fact that if the Committee’s questions are not responded to, one of the options available to the Committee is to call him to give evidence in person.”

READ MORE: Nicola Sturgeon challenges Theresa May to Brexit debate

A spokesman for Cook said of the DCMS response: “You got my answer. Richard responded. If they haven’t found it that’s their problem. Don't have time for any further discussion on this matter.”

The Electoral Commission told the DCMS inquiry this month that it was satisfied the £435,000 donation to the DUP was permissible under UK law.

Louise Edwards, the head of regulation at the Commission, said: "We cannot talk about donations to the DUP from that period and the reason for that is because having verified those reports the donors on them were permissible.”

In September, interim Scottish Tory leader Jackson Carlaw backed greater openness from the CRC. Asked if Cook should be transparent about the identity of CRC donors, he said: “From my perspective, yes.”

An SNP spokesperson said: "There are serious questions to answer over how such a large sum of money found its way from the CRC campaign into the hands of the DUP. Richard Cook should help the DCMS committee with their investigations and provide some much needed clarity on the issue."