Alliance party leader Naomi Long. Picture by Mal McCann

THE DUP paid almost £33,000 during the EU referendum campaign to a Canadian firm linked to Donald Trump's billionaire backers that 'micro-targets' voters on social media.

AggregrateIQ received the money last year as part of £425,000 spent by the party supporting a Leave vote.

The data analytics firm received a total of £3.9m from the official Leave campaign and a further £757,750 from other officially registered campaigns backing Brexit – more than any other company in the referendum.

It has led to questions over how separate Leave campaigns each began using a largely unknown technology firm, and its potential impact on the referendum outcome.

'Coordination' between campaigns without declaring expenditure jointly is prohibited under electoral law.

The Electoral Commission has launched an investigation into the spending return of Leave.EU, one of several registered Brexit campaigns.

The DUP last night said it "complied with all legal requirements relating to the referendum campaign".

The Electoral Commission also said it has "has not seen evidence to suggest that the party may have broken the joint campaigning rules".

However, Alliance leader Naomi Long said "serious questions need to be answered" by the DUP.

"Coordination between different Leave campaigns without joint declaration of spending would be a clear breach of the law," she said.

"Serious questions need to be answered as to how the DUP made the choice to purchase services from AggregateIQ, which allegedly had no web presence in 2016, and yet were commissioned to do work supposedly independently by a number of organisations in the Leave campaign."

AggregrateIQ is thought to have 'micro-targeted' voters with political advertising on social media using their personal data.

In a report in the Observer newspaper on Sunday, the firm is said to be linked to one of Donald Trump's biggest donors and was also involved in his campaign to become US president.

A privacy watchdog, the Information Commissioner's Office, is currently examining how personal data is being used by data analytics companies for work such as political campaigns.

The concerns follow questions raised in February about the DUP's Brexit campaign being financed by the Constitutional Research Council (CRC) – a group of pro-union business figures chaired by a former vice chairman of the Scottish Conservative Party.

More than half of its funding was spent on a £282,000 front-page wraparound advertisement in British newspaper Metro – a publication not circulated in Northern Ireland.

The DUP insisted it was "giving total transparency", but open democracy campaigners claimed the party's disclosure about CRC "merely opened one curtain to reveal another behind it".

Mrs Long said last night: "The choice of these and other contractors by the DUP and others, and the commissioning of GB-only Metro wraparound adverts, which complemented other parts of the Leave campaign in GB, all supposedly with no co-ordination, requires proper and full investigation.

"The law is there to ensure no-one can buy an election and I welcome the investigations into the alleged co-ordination and misuse of personal data.

"This highlights yet again why we need full openness and transparency regarding political donations here."

Green Party deputy leader Clare Bailey also said: "The DUP must explain their relationship with AggregateIQ and what the firm provided in return for a £32,750 spend.

"In the interests of transparency and democracy, the DUP should have no problem in providing this information.

"I also believe that the scope of the Electoral Commission must be extended so that international 'consultancy firms' cannot subvert the rules that govern our democratic process through the use of new technology."

The DUP last night refused to explain what it paid AggregateIQ for during its Brexit campaign.

But a party spokesman said: "The DUP complied with all legal requirements relating to the referendum campaign and all spending was properly registered with the Electoral Commission."