Rishi Sunak racked up a £38,500 bill jetting between Tory party events in Wales and Scotland.
The latest register of member's interest show the Prime Minister and his eight-strong entourage were flown to the Scottish and Welsh Conservative conferences by private plane on April 28.
The luxury air travel was funded by Tory donor Akhil Triapathi, according to Mr Sunak's declaration in the register.
A spokeswoman for the PM said the details were all declared in the normal way.
The PM gave speeches to the party's annual conferences in Glasgow and Newport that day, where he came under fire for dodging scrutiny.
No10 got into a row with Scottish political journalists for trying to restrict access to a briefing to handpicked outlets - before caving to pressure after a bitter stand-off.
In Wales, Mr Sunak was criticised for refusing to take questions from Welsh journalists at the conference.
The Prime Minister's love of luxury short-haul flights has been repeatedly criticised during his first seven months in office.
In January, he took a taxpayer-funded private jet to Scotland to launch “green” tax breaks.
He also used the plane to go on a jaunt around Tory target seats in the North of England, and to visit a medical practice in Leeds, in the same month.
In May, Mr Sunak flew on a government chopper to Southampton - a journey that would have taken little more than an hour by rail.
The Prime Minister's spokesman defended the helicopter trip at the time, saying: "His transport will vary depending on his time and where he's going to make the best use of both his time and in the interest of the taxpayer.
"Obviously there's a lot of pressure on his time and he wants to make the most effective use of that time. Sometimes being able to get to and from places quickly is useful."
No10 was unable to say when Mr Sunak last travelled by train.
