THE Electoral Commission has said it will not be opening an investigation into allegations surrounding the DUP's EU referendum campaign.
It concluded it "does not have grounds to open an investigation" into claims of failing to declare joint spending with other pro-Brexit campaigns.
But on concerns over a mystery £435,000 donation bankrolling the DUP's campaign, the watchdog urged the British government to permit it to publish details of pre-July 2017 donations to Northern Ireland parties.
The decision was in response to allegations in a BBC Spotlight programme which examined the DUP's Brexit campaign.
The DUP last night accused the corporation of anti-Brexit "political bias", but the BBC defended its journalism.
Questions have persisted over apparent links between the DUP's campaign and Vote Leave, the official Leave campaign during the 2016 referendum on whether the UK should stay in the European Union.
'Coordination' between campaigns without jointly declaring expenditure is prohibited under electoral law – a measure designed to ensure legal spending limits are not side-stepped through front groups.
Last month the Commission fined Vote Leave £61,000 and referred senior figures to police after finding its £7m spending limit was breached by funnelling £675,315 through youth group BeLeave.
The Commission found that BeLeave spent the money on Canadian data analytics firm AggregateIQ under "a common plan with Vote Leave", which was not declared by Vote Leave and took its spending over the limit by almost £500,000.
Other Brexit-backing groups also used AggregateIQ during the referendum campaign. They included the DUP, which spent almost £33,000 on the firm.
DUP deputy leader Nigel Dodds was a director of Vote Leave.
Vote Leave canvassers were spotted using DUP Brexit placards, while both campaigns both used the same printing company. The DUP also received £723 from Vote Leave for advertising.
DUP Belfast councillor Lee Reynolds also oversaw Vote Leave's campaign in Northern Ireland.
In June, BBC Spotlight revealed AggregateIQ had said its contact for the DUP campaign was Mr Reynolds.
Cyber security expert Chris Vickery, who examined AggregateIQ datasets, also told the programme he found numerous references to Vote Leave-related work but none relating to the DUP.
The programme also investigated the man heading an unknown pro-union group which bankrolled the DUP's Brexit campaign.
The DUP received around £435,000 from the Constitutional Research Council (CRC), which has been described as a group of pro-union business figures. The party used £425,000 on its campaign and transferred the rest to normal party funds.
More than half was spent on a front-page wraparound advertisement in London-based newspaper Metro – a publication not circulated in Northern Ireland.
CRC's only known member is its chair Richard Cook, a former vice chairman of the Scottish Conservative Party.
The DUP has said the party authorised and directed all spending, and complied with electoral law at all times.
Following the Spotlight programme, the Electoral Commission contacted the BBC Northern Ireland seeking further information.
After being told there was no "significant information" other than what was in the programme, the Commission said it considered whether other evidence sources were available.
In a statement today, the watchdog said it concluded it "does not have grounds to open an investigation into the allegations made".
It said under the rules set out by the British parliament, certain forms of 'joint working' are permitted. These are donations from an individual or group to multiple campaigners; a single supplier working for multiple campaigners; and individuals volunteering for multiple campaigners.
The watchdog added: "The Commission continues to be prohibited by legislation from disclosing any information concerning donations to Northern Ireland recipients made prior to July 1 2017.
"We continue to urge the UK government to bring forward legislation that will enable us to publish information on donations from January 2014."
Alliance deputy leader Stephen Farry said the Commission's conclusion does not exonerate the DUP.
"This decision does not constitute an exoneration of the DUP but rather highlights the lack of robustness of the law, practice and accountability regarding the regulation election campaigns and referendums," he said.
"The Electoral Commission appear to not be able to do more within the existing legal framework."
The DUP said the Spotlight programme was "heavy with innuendo but light on facts", and the BBC had "serious questions to answer about its bias against those who voted to leave the EU".
DUP MP Gregory Campbell also accused the BBC of "political bias".
In response a BBC spokeswoman said: "This Spotlight investigation raised important issues of public interest and was made in accordance with the BBC's editorial guidelines, including those relating to accuracy and independence.
"It was carefully and extensively researched and put significant evidence into the public domain."
