European Union officials are concerned about British Prime Minister Boris Johnson's use of "offensive" language in parliament, notably words like "surrender", "betrayal" and "traitor."

Taking to Twitter, the EU commissioner in charge of security issues — U.K. national Julian King — describes Johnson's choice of words as "crass and dangerous."

King says that "if you think extreme language doesn't fuel political violence across Europe, including U.K., then you're not paying attention."

EU commission spokeswoman Mina Andreeva says "respect is the key word" in political debate.

She told reporters Thursday that "respect is a fundamental value in all democracies. It is the responsibility of each and every politician to uphold our values, and history has shown us what happens when they are not respected."