Allegedly Tony Blair told his friend Shirley Williams that Bush said this. Snopes claims this is false based on Alastair Campbell's [Blair’s director of communications and strategy] say-so. https://www.snopes.com/fact-check/french-lesson/

He says “I can tell you that the prime minister [Blair] never heard George Bush say that, and he certainly never told [his friend] Shirley Williams that President Bush did say it. If she put this in a speech, it must have been a joke.”

While Blair / Campbell have an obvious interest in denying this (it's not good to be rude about other countries leaders), we might reasonably be suspicious of Campbell's denial.