A City firm co-founded by the influential Conservative backbencher, Jacob Rees-Mogg, has set up an investment fund in Ireland and is warning prospective clients about the financial dangers of the sort of hard Brexit favoured by the Tory MP.

London-based Somerset Capital Management (SCM) described Brexit as a risk in a prospectus to a new fund it launched in March, which has been marketed to international investors who want to keep their money in the EU long-term.

The disclosure is embarrassing for Rees-Mogg, who works part time at Somerset Capital in addition to his work as an MP. The parliamentarian has repeatedly dismissed the concerns of those worried about the financial risks of Brexit and has argued the UK needs to quit the single market and customs union so the country is not a “rule taker” from Brussels.

But in reference to Brexit, the SCM prospectus warned: “During, and possibly after, this period there is likely to be considerable uncertainty as to the position of the UK and the arrangements which will apply to its relationships with the EU.”

The document continued: “As [the firm is] based in the UK and a fund’s investments may be located in the UK or the EU, a fund may as a result be affected by the events described above.”

Rees-Mogg is a non-executive chair at SCM and is paid about £14,000-a-month for working 30 hours a month there. Earlier on Wednesday, he defended the decision by the investment firm to create a new investment fund in Ireland.

“A number of existing and prospective clients requested domiciled access to Somerset’s products,” he told the Daily Telegraph. “The decision to launch the fund was nothing whatsoever to do with Brexit.”

Rees-Mogg said that SCM had funds based across the world and that “people outside the EU are used to Irish domiciled funds”. The warnings in the prospectus, he said, were “not a policy statement by SCM”, but guidance to investors that was drafted by lawyers.

He has complained about “endless scare-stories about project fear”. In February, he was a signatory to a letter to the prime minister, Theresa May, demanding a hard Brexit that was described by one party colleague as a “ransom note”.

The MPs chairs the powerful European Research Group, which has consistently sought to put pressure on May to adopt a more antagonistic stance towards Brussels as the UK negotiates its exit from the bloc.