Boris Johnson, the British foreign secretary and former London mayor, has renounced his U.S. citizenship, according to recently released tax data .

Though thoroughly British -- a member of Parliament and educated at Oxford -- Johnson was born in New York. At the time of his birth, his father, British author Stanley Johnson, was studying at Columbia .

Johnson in 2014 complained about an Internal Revenue Service tax bill on the sale of a London house, calling the fees "outrageous."

As London mayor, he took a leadership role in the city's 2012 Olympics. A former journalist, Johnson is now known in Europe as a bombastic and colorful politician, with a personal life highly scrutinized in the press . A prominent supporter of British exit from the European Union, it was thought he would be a candidate for prime minister last year, before political machinations suddenly forced him out of the race . When Theresa May became prime minister, she asked him to serve as foreign secretary .

He joins a number of people who are renouncing American citizenship, among the most coveted passports in the world. Expatriation is not new, but the number of people renouncing their formal U.S. ties has seen an uptick in recent years . Before 2011, less than 1,000 people annually expatriated. In the final quarter alone of 2016, however, more than 2,300 went through the process.

It has been pointed out that it's possible Donald Trump's election as president is contributing to the rise. A number of prominent figures pledged to leave the country if the New York mogul won last November.

Attorneys Andrew Mitchel and Ryan Dunn highlight taxation as another motive.

"The escalation of offshore penalties over the last 20 years is likely contributing to the increased incidence of expatriation," the two write on International Tax Blog .

Johnson has been weary of Trump in the past, but has increasingly defended working with him since he won election. The issue of Trump being afforded a state visit is particularly contentious in the United Kingdom. Johnson, the top diplomat for May's government, says he should.