LONDON — The letter is as British as it gets: polite, polished and understated.

Written by a senior Conservative Party lawmaker, Christopher Heaton-Harris, and sent to British universities, it asked officials to reveal the names of professors involved in teaching students about Europe, including Britain’s decision last year to leave the European Union, a process known as Brexit.

“Furthermore,” the missive read, “if I could be provided with a copy of the syllabus and links to the online lectures which relate to this area I would be much obliged.”

Despite its apparently mild tone, the letter has provoked a national debate on freedom of speech in universities and whether the country is being subjected to political censorship in a British version of McCarthyism.

The uproar increased on Thursday after The Daily Mail, a popular tabloid that has vociferously supported Brexit and which carries an anti-immigrant slant, published a front-page article citing instances in which it said university professors had encouraged students to oppose a Brexit. On another page, more than a dozen headshots of academic leaders were assembled around a headline that read: “Just why is every new Oxbridge head a leftie?” (“Oxbridge” is shorthand for the two leading universities in Britain: Oxford and Cambridge.)