Sir Keir Starmer flew in a private jet paid for by Qatar to visit the country's leader last month, according to parliamentary records.
The Labour leader made a return trip to the kingdom whilst attending the COP28 climate conference held in Dubai.
His latest declaration of financial interests shows the trip for him and three staffers cost £25,508.
The COP28 organisers also paid £765 for him to travel by car at the conference.
A spokesperson for the Labour leader said: "Keir Starmer was pleased to accept an invitation from His Highness The Emir of Qatar. Their conversation focused on the current crisis in the Middle East."
Sir Keir has previously said he attended the COP summit, hosted by the United Arab Emirates in its largest city of Dubai, in his capacity as Labour leader.
He defended his attendance as a non-government figure, saying it was "in the British national interest" for him to go.
"If there is an election next year that we are privileged enough to win, then it's very important that we go all-out for clean power [in] 2030," he added.
He has also said he used his meeting with the Emir of Qatar in Doha, the country's capital, to discuss the situation in Gaza as well as the "vital cooperation" between Qatar and the UK.
Now his latest declaration shows his return journey there from Dubai was paid for by Qatar's Ministry of Foreign Affairs.
The return specifies that the journey was made in a "private jet" - although the type and owner of the aircraft is not specified.
Labour has previously vowed to curb the use of UK-funded private jets by ministers undertaking official trips to "save millions of pounds" for British taxpayers.
In a speech to the party's autumn conference, shadow chancellor Rachel Reeves attacked Prime Minister Rishi Sunak's "private jet habit".
Although the trip to Doha was not funded by British taxpayers, it could prove awkward for Sir Keir, with climate campaigners criticising Mr Sunak for making trips in private planes on climate grounds.
The direct flight from Dubai to Doha takes around an hour and a half, with regular commercial flights between the two cities.
