WASHINGTON, United States (AFP) — A dramatic leadership struggle in the most powerful US gun-owners organisation has resulted in its p resident Oliver North saying Saturday that he will not serve a second term.

North, who gained international notoriety as a key figure in the Iran-Contra arms scandal under President Ronald Reagan, was forced out as president of the influential National Rifle Association by the group’s long-time CEO, Wayne LaPierre.

An NRA board member, Richard Childress, read a letter from North at the group’s annual convention in which North said his efforts to fight alleged financial mismanagement in the NRA had led to his ouster.

North, who became president only last year, alleged in a letter to the NRA’s executive committee that LaPierre had purchased more than $200,000 in personal items and charged them to a vendor, The Washington Post reported.

North called for the NRA to establish a committee to review the group’s finances.

LaPierre put a different light on the men’s differences, accusing North of issuing a blunt ultimatum to either “resign or there will be destructive allegations made against me and the NRA”, LaPierre said in a letter published Friday by the Wall Street Journal.

LaPierre said the threat “alarmed and disgusted” him.

Amid the bitter internal spat, the NRA meanwhile has filed a lawsuit against its advertising agency Ackerman McQueen, complaining of unjustified billings. Ackerman employs North to host a TV show called American Heroes.

The firm called the suit “frivolous (and) inaccurate”.

The leadership struggle has played out in public view at a time when the NRA — which has long played an outsized role in the gun debate in America — has faced mounting political, regulatory and financial challenges.

After recent years saw some of the worst mass shootings in US history, leading to new cries for gun control, the pro-gun group’s revenues dropped sharply last year.

Regulators in New York, meantime, have threatened to examine the group’s tax-exempt status.

But President Donald Trump has thrown his strong support to the group. In 2017 he became the first US president since Reagan to address the NRA, and he did so again on Friday at its Indianapolis convention.

North has long been a popular figure among American conservatives, despite — or perhaps because of — his involvement in the Iran-Contra scandal.

A retired Marine Corps lieutenant colonel who went to work in the Reagan White House, he was convicted in 1989 on three charges linked to the Iran-Contra scheme, under which money from arms sales to Tehran was funneled to rebels in Nicaragua. The convictions were later overturned.

LaPierre himself had warm words for North when he was tapped as the group’s next president last year.

“Oliver North is a legendary warrior for American freedom, a gifted communicator and skilled leader,” LaPierre said in a statement.

“In these times, I can think of no one better suited to serve as our president.”