The prominent backbencher, who some Eurosceptics want to see succeed Theresa May as Tory leader, will next month speak at an event organised by North Antrim MP Ian Paisley which will raise money for Arlene Foster’s party.

However, local Conservatives have denounced the move and asked Conservative chairman Brandon Lewis to investigate how Mr Rees-Mogg is raising money for a party which will be standing against the Tories in May’s council elections.

In a letter to Frank Shivers, former deputy chairman of the NI Conservatives, Mr Rees-Mogg was explicit about the purpose of his visit.

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Jacob Rees-Mogg is a key Brexiteer who shares some ground with the DUP

In the letter, which has been obtained by the News Letter, the North East Somerset MP did not respond to an invitation from Mr Shivers to fundraise for the Conservative Party in Northern Ireland.

In the letter, which was sent last month, Mr Rees-Mogg said: “As you are aware, I am visiting Northern Ireland in January for a dinner with the Democratic Unionist Party.

“As we are currently working closely with the DUP in Parliament I am happy to do a fundraiser for them. I wish you every success with you future campaigning.”

Mr Rees-Mogg is the latest in a long line of senior Tories to have come to Northern Ireland for fundraising or other events organised by the DUP, including Defence Secretary Gavin Williamson, who attended a dinner hosted by Arlene Foster, and Environment Secretary Michael Gove, who spoke at a fundraiser for Ian Paisley in north Antrim.

However, Mr Gove denied that he was aware that it was a DUP fundraiser, unlike Mr Rees-Mogg who has been open about the purpose of the event.

Mr Shivers said that he had approached Mr Rees-Mogg at the Conservative conference in Birmingham in the autumn and it was there that the MP told him that he was coming to raise money for the DUP in January.

Mr Shivers said that during a robust conversation he had pressed Mr Rees-Mogg to do the same for the NI Conservatives and then had followed that up by writing to the MP.

He said that in conversation Mr Rees-Mogg had described the Tories’ arrangement with the DUP as a “coalition”, something which is not the case because the parties have a confidence and supply deal, a looser agreement.

However, Mr Shivers said he had pointed out that even when the Tories were in coalition with the Liberal Democrats it would have been unthinkable for a senior Tory to raise funds for what was a rival party.

Mr Shivers said it was “disrespectful” for senior party colleagues to come to be fundraising for the DUP.

He claimed that the DUP fundraising events were in some cases raising “in excess of £30,000” – a huge sum in Northern Ireland politics – while “we’re relying on our members giving contributions”.

However, DUP MP Jim Shannon, who has been instrumental in bringing many senior Tories – including Andrea Leadsom and Julian Lewis – to DUP events, said he “would be amazed if that was the case”.

Mr Shannon, who will have another senior Brexiteer backbencher, Peter Bone, at a DUP event in his Strangford constituency in February, said that in his case he splits the money raised at the event evenly between the DUP and Elim Missions.

He highlighted that the party had also brought over Labour MPs such as Kate Hoey and Stephen Pound, something he said was part of “building relationships” at Westminster and which had been going on for years.

Mr Shivers said he was “extremely disappointed by fellow Conservatives” coming and “raising funds for our electoral competitors”. He said: “We certainly seem to be the poor cousins.”

The event is also further evidence of the growing links between the DUP and leading Tory Eurosceptics. The party has been working increasingly closely with the anti-EU European Research Group of which Mr Rees-Mogg is a leading member, and last month gave a rapturous welcome to former foreign secretary Boris Johnson when he addressed the DUP conference.