Alan McFarland believes his military background will serve him well

Former British army major Alan McFarland, 55, said his military background would help him unite the party and instil necessary discipline.

He will face challenges from fellow MLAs Sir Reg Empey and David McNarry when the Ulster Unionist Council meets on 24 June to elect a new leader.

Mr McFarland told a news conference he was leading "a grass roots rebellion".

Mr Trimble resigned when the party lost all but one of its MPs in the election.

Mr McFarland, who has the backing of the party's sole MP Sylvia Hermon, said the members had shown they had enough of "cabals and cliques and enough of the culture of being led by the anonymous and unaccountable".

In an obvious swipe at Sir Reg and David McNarry, he said: "I have never been a party officer and I have never been an advisor to the leadership."

I believe I can reshape and reinvigorate the Ulster Unionist Party into a strong, election-winning machine Alan McFarland UUP leadership challenger Slugging it out to be UUP leader

Entering the leadership race, Mr McFarland said the election results showed that "a large part of the unionist electorate has lost confidence in the Ulster Unionist Party".

He added: "They either stayed at home or supported the DUP.

"If the UUP is to rebuild confidence and trust, it must look like a party that deserves a vote - not one riven with internal squabbles and a bad sense of judgement on political PR issues.

"To that end, our internal structures need to be improved and a tight sense of self-discipline introduced.

"The party also has to rededicate itself to 'bread and butter' politics out there in the community.

"We have to matter, to make a difference and to improve the lives of individuals in our society."

Mr McFarland said the combination of his training at the Royal Military Academy at Sandhurst, along with his 18-year career in the Army and experience as a management consultant, meant he was well equipped to lead the UUP.

He added: "With these skills and an apprenticeship of 13 years with the party, as a staff member, North Down Association officer and an elected representative, I believe I can reshape and reinvigorate the Ulster Unionist Party into a strong, election-winning machine."