Jeffrey Donaldson, DUP Brexit campaign manager.

Democratic Unionist Party politician Jeffrey Donaldson has said that he couldn’t remember why his party choose to spend more than £32,000 during the Brexit campaign on a controversial data analytics company linked to Donald Trump.

The DUP paid £32,750 to Aggregate IQ, an obscure data analytics company based in British Columbia, Canada, according to accounts filed with the Electoral Commission. This money was to target voters on social media during the Brexit referendum campaign. But DUP Brexit campaign manager Jeffrey Donaldson could not tell us how he discovered Aggregate IQ, a company that had almost no online presence last June.

“I’m afraid I don’t have the files in front of me, so I’ll have to check the records for you,” the Lagan Valley MP said. “I think it was an internal recommendation,” Donaldson added.

Why a political party in Northern Ireland decided to spend more than half its budget for the 2015 general election with an unheard of data analytics company in Canada is not clear. But what we do know is that more money was spent with AggregateIQ than with any other company in any other campaign in the entire referendum. Vote Leave, the official leave campaign, spent £3.9m with the company.

An on-going Observer investigation has found that Aggregate IQ has very close ties to Cambridge Analytica and hedge fund billionaire and Donald Trump-backer Robert Mercer. Cambridge Analytica have been credited by some with “psychological warfare techniques” to help swing the US presidential election in Trump’s favour.

Earlier this year, openDemocracy revealed how more than £435,000 was funneled into the DUP’s Brexit campaign. Under Northern Irish electoral law, the source of this dark money has remained secret but we do know that money came through the Constitutional Research Council, a shadowy group chaired by Richard Cook, a former vice chairman of the Scottish Conservative and Unionist Party.

Co-ordination between campaign groups is illegal under UK electoral law unless their expenditure is counted together – a law designed to ensure that no one can get around campaign spending limits by setting up front groups. Aside from the official Vote Leave campaign, three affiliated leave campaigns – BeLeave, Veterans for Britain and the Democratic Unionist party – spent a total of £757,750 with Aggregate IQ. The Observer asked Veterans for Britain where they heard about Aggregate IQ. David Banks Veterans for Britain head of communications said: “I didn’t find AggegrateIQ. They found us. They rang us up and pitched us.”

Both the DUP and Vote Leave has denied any co-ordination between the two campaigns. Lee Reynolds, a DUP staffer in Belfast who took a break from the party to oversee the official Vote Leave campaign in Northern Ireland denied recommending Aggregate IQ to the DUP. “I wasn’t co-operating with the DUP I was working for Vote Leave at the time,” Reynolds told openDemocracy. DUP North Belfast MP Nigel Dodds was a board member of Vote Leave.

The £435,000 donation given to the DUP’s Brexit campaign has been the source of on-going controversy. In the run-up to March’s Northern Irish assembly elections DUP leader Arlene Foster denied knowing the size of the donation or the specific source. Jeffrey Donaldson has admitted to openDemocracy that he did not know about the links between Richard Cook and Saudi intelligence services.

Under Northern Irish electoral law, donor identities are secret but campaign spending is declared. Details of the DUP’s spending with Aggregate IQ were released by the Electoral Commission earlier this year. Privately, the DUP lobbied the Electoral Commission against releasing this information. After the Brexit vote, the DUP transferred £9,000 remaining from the donation it received for its Brexit campaign into normal party funds.