A Trump appointee is facing calls for an investigation into allegations he tried to divert scarce firefighting resources to tackle a small blaze near his ranch.

Michael Boren, the undersecretary of agriculture for natural resources and environment, reportedly asked for more aircraft to douse a seven-acre fire near his 480-acre “Hell Roaring” ranch in Idaho, which is worth an estimated $4.3m (£3.2m).

The request was despite much larger fires over a similar period not receiving “even a fraction of the same commitment of resources”, three Democrat senators demanding the investigation said.

The fire was caused by an unattended campfire on July 12 and was fully contained three days later, according to officials.

The Washington Post reported that the billionaire, who co-founded financial technology firm Clearwater Analytics, called Forest Service officials several times, asking why more aircraft had not been sent to tackle the fire.

He was told firefighting planes were not needed to tackle the inferno, which was easily reachable from the ground.

But Mr Boren “was on the phone calling people that day asking why there weren’t more resources on the fire and when there was going to be more”, the Post added.

Some aircraft were eventually diverted from other parts of the state after Mr Boren’s intervention, the Post reported.

On the same day, major wildfires were reported in nearby Utah and Colorado.

Three Democratic senators – Ron Wyden, Amy Klobuchar and Martin Heinrich – have demanded an explanation from Brooke Rollins, the US agricultural secretary and Mr Boren’s chief.

They wrote: “We request a full investigation into the nature and extent of Boren’s involvement in response to the Cabin Creek Fire and a detailed accounting of the safeguards the agency has implemented or plans to implement to prevent political interference and conflicts of interest in wildfire response.

“The personal interests of political employees should not be a factor that influences the allocation of wildfire resources to communities threatened with devastation.

They added that fires of a much larger size did not receive “even a fraction of the same commitment of resources” and that Mr Boren’s actions constitute potentially “a misuse of taxpayer funds”.

The US agriculture department denied Mr Boren had acted improperly in a statement it issued two weeks ago.

“Mike Boren is expected to have regular contact with the agencies he oversees. The fact that a senior government official would be monitoring and communicating with other government officials about an event he oversees is a non-story.

“Under Secretary Boren did report a fire that was near property he owns, just as one would hope any citizen in an area under threats from wildfires would do. However, at no point did he pressure leadership or order more resources to fight this or any other fire.”