Northern Ireland’s Democratic Unionists will elect their next leader on May 14, an unprecedented contest to run the largest party in the region’s power-sharing government.

The first leadership ballot in the DUP’s 50-year history will be between Stormont’s agriculture minister Edwin Poots, Westminster MP Sir Jeffrey Donaldson and anyone else who enters the race before 5pm on Thursday, the party said on Tuesday.

The contest was trigged by a dramatic move against current leader Arlene Foster, who also holds the position of Northern Ireland’s first minister.

Foster was unopposed when she took over from Peter Robinson in December 2015, as was Robinson when he succeeded DUP founder Ian Paisley in 2009.

Lord Nigel Dodds said on Tuesday night that he had decided to step down as DUP deputy leader “whenever the next internal election cycle occurred” following his 2020 elevation to the House of Lords. Peers cannot vote in DUP leadership elections and so he said it would be “incongruous and inappropriate” for him to remain in the party’s leadership team.

The party will hold a virtual meeting on Friday May 14 to count votes for leader and deputy leader.

Votes can be cast by all DUP members who are either members of Northern Ireland’s legislative assembly or the House of Commons, a group of 36 including Foster. A result is expected by 5pm that evening.

The DUP’s handling of Brexit was the biggest policy issue that led to Foster’s ousting, with party members railing against a customs border in the Irish Sea that was imposed as a way of keeping open borders between Northern Ireland, outside the EU, and the Republic, within it.

Some also felt that Foster was too liberal on social issues, as highlighted by her recent decision to abstain in a recent Stormont vote banning gay conversion therapy, which was opposed by her DUP colleagues.

Poots, a young-earth creationist who rejects the theory of evolution, told the Financial Times that if he won the DUP leadership he would not take the first minister role and might not stay on as agriculture minister. “I need to focus on the party,” he said. “That’s what I need to expend my energy on.”

The first minister would be selected after consulting with the wider party, he said. “It’s a very significant role,” he said, adding that he had “nobody in particular in mind”. He dismissed reports that he would try to install Lagan Valley assembly member Paul Givan.

Poots has already signalled a harder line on the Northern Ireland protocol that governs post-Brexit trade between Northern Ireland and Great Britain, telling colleagues of plans to consider seeking a judicial review of the arrangement. Poots told the FT he was exploring the judicial review in his current role as agriculture minister and would make a decision on it once he had received legal advice “in another couple of weeks”.

Ulster Unionist regional assembly member Doug Beattie said on Tuesday, that “whoever takes over as [DUP] leader, the protocol has the DUP DNA all over it”.

Donaldson, 58, is seen as a more moderate voice. In a video announcing his candidacy on Monday, he said he wanted to “build a shared future for Northern Ireland, where everyone regardless of their background has a part to play in showing the world what we are truly capable of”.

He stressed the need for “positive leadership, strategy and values” and promised an “agreed programme of meaningful reform and clear policy direction on key challenges, such as the protocol”. Since Donaldson is an MP, he would have to resign from Westminster and seek a seat in the legislative assembly to take the role of first minister.