It has entered common usage in the late 2010s as a disparaging term for British people. It's definitely not on the level of the n-word, but it's roughly on par

It has entered common usage in the late 2010s as a disparaging term for British people. It's definitely not on the level of the n-word, but it's roughly on par with calling Germans "krauts", Scots "jocks", Italians "dagos" etc. So it's not like the very worst thing in the world, but it's pretty rude and it's certainly not something you should make a habit of.