Arlene Foster has said a row over a controversial Brexit donation is a “re-heated story” from political opponents to distract from “real issues”.
In February, the DUP confirmed it received a donation of about £435,000 from pro-union business people.
It said £425,000 of the money from the Constitutional Research Council (CRC) was spent on pro-Brexit advertising.
The Electoral Commission said it was not investigating the issue, but Sinn Féin is to meet the commission later.
The party said it wanted to discuss concerns over what it has described as “dark money”.
‘Nothing to see’
The CRC is chaired by Richard Cook, a former vice chairman of the Scottish Conservative and Unionist Party.
There are concerns from the DUP’s political opponents that three donors associated with the CRC have not been named by the DUP.
Arlene Foster told the BBC’s The View programme: “We have satisfied ourselves that it was all kept within the rules, and we are satisfied the money came from UK business people.
“This is a re-heated story. We dealt with it at the time of the Assembly election and here we are dealing with exactly the same thing.
“Sinn Féin are trying to deflect from the real meaning of this election, which is all about the union.”
Mrs Foster was asked if she knew the full identity of the other individuals who gave the money, more than half of which was spent on a double-page pro-Brexit ad in the Metro newspaper, which is not published in Northern Ireland.
She said she did know who had made the donation and she was “satisfied that the people who gave it had every right to give the donation”.
“We have answered all the questions the Electoral Commission have asked us.
“It is satisfied we have done everything in accordance with the law and I am satisfied.
“As far as I’m concerned that’s the end of the matter”.
How the £425,000 was spent
- £282,000 on advertising in Metro newspaper in support of Brexit
- £99,616 on promotional material
- £32,750 with Canadian IT and consultancy firm
- £10,823 spent in Northern Ireland
The DUP leader said there was “no issue” with her judgement.
“Behind all of this, is that people didn’t like that we were part of a national campaign in relation to Brexit and we took our position up as a UK party. There’s nothing to see.
“Sinn Féin has brought millions of pounds into Northern Ireland throughout the years and no-one has known where that money has come from.
“It does frustrate me that we are talking about these issues instead of issues around the union.”
Mrs Foster also spoke about her party’s performance in March’s assembly election.
“The last election was a perfect storm. We were under incredible attacks from all sides. Personally I was being buffeted by everyone.
“The fact that we came out with over 225,000 votes was a good result, given where we were.”
Mrs Foster said she would continue to engage with the Irish language community. In April she met with a number of Irish language groups.
The meetings came after she said in February that her party would never support legislation to give official status to the language.
“I have yet to be convinced there is an need for such an act but we are still talking about it.
“There has been very much a use of Irish language to batter people, we’ve seen it in the chamber and when I meet people who genuinely do love the Irish language and the way they speak to me, through drama or literature, it is different,” she said.