Leaked documents appear to reveal the lavish spending of the National Rifle Association's chief executive Wayne LaPierre, who received luxury clothing and travel expenses paid for by the lobby group's longtime advertising firm Ackerman McQueen.

A memo from the firm claims it spent $542,000 (£415,000) of the NRA's money, which largely comes from contributions and membership fees, on expenses for Mr LaPierre over a 13-year period.

The documents also show that the pro-gun organisation amassed more than $24m in legal fees to an outside counsel, Bill Brewer, over the last year alone, in what former president Oliver North described as an "existential threat to the financial stability of the NRA".

In a statement, the NRA did not deny the authenticity of the documents. It admitted they came from a new leak and called it "pathetic" that someone would pass such information to the media, while at the same time attempting to dismiss it as "stale news".

Mr LaPierre's expenses have previously been reported on, but this is the first time the specific figures have been revealed, according to the Wall Street Journal. They include $275,000 spent at a suit store, and $265,000 on travel.

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Last month, the NRA sued Ackerman McQueen for documents regarding its expenses and bills. The Daily Beast reported that dozens of board members have had access to the documents, and that they could contain further embarrassing revelations.

The leaks are the latest in a string of setbacks for the NRA, including a widely publicised battle with New York State, where the association is based, and which the president has weighed in on.

In a statement, the new NRA president Carolyn Meadows said: “This is stale news—being recycled by those with personal agendas.