So Gordon Brown is at the centre of a controversy for calling a retired resident of Rochdale a “bigot” after she questioned his immigration policy. The leader of the Labour party chose a very interesting word:

1590s, from Fr. bigot (12c.), in O.Fr. “sanctimonious;” supposedly a derogatory name for Normans, the old theory (not universally accepted) being that it springs from their frequent use of O.E. oath bi God. Plausible, since the Eng. were known as goddamns in Joan of Arc’s France, and during World War I Americans serving in France were said to be known as les sommobiches (son of a bitch). But the earliest French use of the word (12c.) is as the name of a people apparently in southern Gaul (which led to the now-doubtful, on phonetic grounds, theory that the word comes from Visigoth). Sp. bigote “mustache” also has been proposed as a source, though the sense is not adequately explained. The earliest English sense is of “religious hypocrite,” especially a female one, and may have been influenced by Beguine. Sense extended 1680s to other than religious opinions.

Etymonline

This term originally referred to a religious hypocrite, but its use has been extended and designates a fanatical adherent or believer; a person characterised by obstinate, intolerant, or strongly partisan beliefs (Oxford English Dictionary). In French, I would translate it by sectaire.
Let’s hope that the party leaders will be able to put the record straight on immigration in the UK during tonight’s debate.