Jacob Rees-Mogg has responded to criticism from former taoiseach (Irish Prime Minister) Bertie Ahern over his knowledge of the Irish border.
In remarks made on Sunday, Mr Ahern said the Conservative MP had admitted not knowing what the Irish border was.
Responding on Twitter, Mr Rees-Mogg, a high-profile supporter of Brexit, said the criticism was “quite funny but regrettably untrue”.
“Perhaps Ireland had a comedian as its leader before Ukraine,” he said.
In a statement to BBC News NI, Mr Rees Mogg added: “I have never had a private conversation with Mr Ahern whom I only met in the confines of a Brexit Select Committee meeting.”
Mr Ahern made the comments at the Women in Media conference in Ballybunion, County Kerry as part of a debate on Brexit.
He was appearing on a panel alongside Dr Mary Murphy, a lecturer with University College Cork, and Mairead McGuinness, who holds the position of first vice-president of the European Parliament.
Mr Ahern said Mr Rees-Mogg, the leader of the European Research Group, was a “strange fish, in and out of the water”.
“The reality is he admitted to me he had no idea of what the border was. I think a lot of British politicians thought the border was something up around Dundalk or Newry, and that there was a gate on it,” he said.
“I mean the idea that it was 460 km across the island and that you could criss-cross it to farms and houses, they just didn’t know it.”
Mr Ahern also criticised the educational background of some of the UK politicians involved in Brexit.
“And regards to the fact that lot of these guys went to Oxford, Cambridge and Eton, they’re not very bright. This is the problem,” he said.
Mr Rees-Mogg attended exclusive public school Eton College, before studying History at Trinity College, Oxford.
Research published by the Sutton Trust in January 2018 found just under half of Theresa May’s cabinet attended either Oxford or Cambridge.
It also found about one third received a private education.
Mr Ahern, who served as taoiseach between 1997 and 2008, was one of the architects of the Good Friday Agreement.
He has been an outspoken critic of the Brexit process.
In January, he described the decision by Theresa May to trigger Article 50 as “absolutely senseless”.
Appearing before Westminster’s Exiting the EU select committee in February, Mr Ahern said there was “no possibility” of the Irish government agreeing that the backstop can be time limited.
The backstop is the insurance policy in the withdrawal agreement to avoid a hard Irish border.
At the conference in County Kerry, Mr Ahern said there was a misconception the backstop was a “massive thousand page document”.