BBC: Boris Johnson's father Stanley says he has become a French national, telling a Belgium news website he wanted to keep "a link" with the EU after Brexit.
Mr Johnson, whose mother was French, told BFMTV getting citizenship was "something precious" and allowed him to "claim part of my identity".
Unlike his son, who led the campaign to leave the EU, Mr Johnson voted Remain in the 2016 Brexit referendum.
However, he later changed his mind saying "the time has come to bail".
Between 1979 and 1984, Mr Johnson was as a member of the European Parliament representing Wight and Hampshire East.
Downing Street said his decision to accept French citizenship was "a personal matter for the prime minister's father".
Mr Johnson announced he would be seeking French citizenship in December 2020 - a month before the UK fully left the EU.
Speaking on Friday, he said he was "very happy", adding: "I count myself once again as a European Union member, that's very good." » | BBC | Friday, May 20, 2022
PM’s father Stanley Johnson ‘secures French citizenship’: Johnson campaigned for UK to remain in EU in 2016 but has since expressed support for Brexit »
Le père de Boris Johnson, Stanley, obtient la nationalité française : Le père du premier ministre britannique Boris Johnson, Stanley, 81 ans, a obtenu mercredi la nationalité française, a-t-on appris jeudi 19 mai auprès du ministère français de la Justice. »
Such hypocrisy! These entitled dudes want all the privileges themselves, but have been absolutely determined to strip such privileges away from the ‘little people’! Fie on them; and fie on this hypocritical dude, too! This is truly sickening. He’s got a face of brass, that’s all I can say. – © Mark