White House staff were warned last month not to use insider information to place bets on prediction markets.

The email was sent to staff on 24 March, a day after US President Donald Trump announced a five-day pause on his threat to attack Iranian power plants and energy infrastructure.

It referred to press reports raising concerns that government officials were using non-public information to place bets on platforms like Kalshi or Polymarket.

White House spokesman Davis Ingle told the BBC that "any implication that Administration officials are engaged in such activity without evidence is baseless and irresponsible reporting."

The Wall Street Journal first reported the email on Thursday.

Ingle also said that all federal employees are subject to government ethics guidelines that prohibit the use of insider information for financial gain.

"The only special interest that will ever guide President Trump is the best interest of the American people," he added.

The BBC has contacted Kalshi and Polymarket for comment.

Polymarket came under scrutiny in January after a gambler made nearly half a million dollars on the capture of Venezuelan president Nicolás Maduro just before it was officially announced.

It was unclear who placed the bet. The anonymous account had a blockchain identifier of letters and numbers.

The incident raised concerns about whether they had benefited from inside information about the US military operation.

Predictions markets, which host more than $44bn (£33bn) in trades, have become increasingly popular in the past year.

The predictions can be related to anything. They mostly involve sports, but users can also place bets on whether, for instance, the US central bank will cut rates or the results of local elections.

Prediction market bets on conflicts have fuelled debate over how the industry should be regulated.

This week, US Congressman Ritchie Torres, a Democrat who sits on the House Financial Services Committee, sent a letter to the Commodity Futures Trading Commission that called for an investigation into "suspicious" trades.

The commission regulates the derivatives trading, which includes prediction markets.

In March, Democrat leaders introduced legislation that would completely ban prediction market betting related to war or military action.

"Corruption and exploitation are thriving right now within the gaps and loopholes of prediction markets," said US Senator Andy Kim from New Jersey.

"This manipulation leaves the select few winning big, at the expense of working Americans," he said.