WASHINGTON (Reuters) - A senior lawyer at the U.S. Treasury Departments Office of the Inspector General said on Thursday he found no violation of law in Treasury Secretary Steven Mnuchins use of private jets for seven official trips, but called for better cases to be made in future for such travel by Trump administration officials.

But the report by OIG counsel Rich Delmar found the department offered insufficient justification for the use of a government plane and recommended future requests provide more detail.

Mnuchins use of a plane at taxpayer expense to travel to Kentucky in August with his wife to view the solar eclipse and speak to business leaders prompted an outcry from Democratic party lawmakers and spurred the Treasurys watchdog agency to examine whether it violated travel or ethics policies.

Cabinet members rarely use government planes or chartered aircraft for domestic travel, but the practice has received significant attention in the wake of Mnuchins trip.

On Friday, former U.S. Health and Human Services Secretary Tom Price resigned after an outcry over his use of private charter planes for government business at a cost of nearly $52,000.

Mnuchin said on Sunday he did not regret using a government plane for the Kentucky trip, calling it completely justifiable.

It was approved by the White House and there were reasons why we needed to use that plane that are completely justifiable, he said on NBCs Meet the Press program.

Mnuchin told NBC that he would only use a private plane for government purposes if either there was a national security issue or we couldnt get somewhere.

The Treasury Department has described Mnuchins trip in August as official government travel. Mnuchin spoke to business leaders in Louisville and visited Fort Knox, the site of significant U.S. gold reserves.

Mnuchin and his wife, Louise Linton, also viewed the Aug. 21 solar eclipse in Kentucky with Senate Majority Leader Mitch McConnell and others.

Public uproar over the trip began to mount after Linton posted a photo of herself deboarding the plane on social media and listed the expensive designer brands she was wearing in the caption.

I recommend that the OIG advise that future requests be ready to justify government air in greater detail, especially regarding cost comparisons and needs for security and other special factors, Delmar said in his report.

(Reporting by Eric Walsh)