The DUP has received a further £13K in donations from the pro-Brexit group who supported the party with over £400k ahead of the EU referendum.
The Constitutional Research Council (CRC) donated £435k to the party during the Brexit campaign, £282,000 of the money was spent on an advert in the Metro newspaper
New documents show that the party accepted a further £13k in donations from the CRC in the months following the referendum.
In October 2016, the DUP received a £6k donation, followed by a further £7k donation in March 2017.
The DUP has told the BBC that it used the donations to "further the cause of unionism at home and abroad" and complied with electoral law at all times.
CRC is chaired by Scottish Conservative Richard Cook, but the identities of those who make donations to the group remain unknown.
The latest donation came to light through Electoral Commission (EC) documents, which were published by the campaign group, the Good Law Project.
The original £435k donation was not reported to the EC, but they accepted that the donation and it's donors were permissable.
A BBC Spotlight programme investigated the donation, but the EC ruled that there were "no grounds" for an investigation into the issue.
The most recent donations were both declared to the EC.
Sinn Fein MEP Martina Anderson said the latest donation raised questions about who was behind the donations.
“The DUP and CRC have never revealed where this money came from and people are rightly asking why that should be the case," she said.
“The public have a right to integrity and transparency in their elected political parties so the DUP leadership should explain the source of these funds."