A trade union activist is entering the race for Labour’s ruling body by running on a pro-single market ticket and leaving the door open to remaining in the EU.

Nick Donovan, the son of a carpenter who previously held a senior role in the Royal British Legion, is launching a campaign for the national executive committee this week as an independent candidate.

His pitch is highly sceptical of Brexit, which he describes as “the most serious crisis faced by the UK since Iraq”, and he says any decision to leave the European single market is “inconsistent” with Labour’s anti-austerity agenda.

Donovan is a surprise entry into the race, which so far has been dominated by the left-wing slate of Jon Lansman, Yasmine Dar and Rachel Garnham, who are going up against comedian Eddie Izzard, Johanna Baxter, a former NEC rep, and Gurinder Singh Josan, vice-chair of Sikhs for Labour.

Today Donovan told LabourList he would be a voice for party members who want Britain to remain in the single market and customs union and would support efforts to “keep the door open” to a second referendum on the final Brexit deal.

“In plain English: hard Brexit results in fewer jobs and lower wages for ordinary workers,” he said.

“The Treasury’s own secret Brexit analysis likely estimates the tax loss of a hard Brexit at £36bn to £45bn every year, roughly a quarter to a third of the NHS budget. Yet, after the transition period, that is the direction current Labour policy is also taking us.

“We can’t both oppose austerity and plan for the hard Brexit of leaving the European Economic Area – it will hobble any future Labour government’s spending plans, and cause us serious problems in Northern Ireland. I want to join the NEC to make that point, politely but persistently.”

Donovan is a member of Unite, vice-chair of his constituency Labour Party and sits on the advisory board of the Labour Campaign for the Single Market.