LONDON—The U.K. is set to face some of the worst strikes in at least a decade, raising fears that a “winter of discontent” will hit the country as workers push for bigger pay raises amid double-digit inflation and a gloomy economic outlook.

University professors, teachers, railway staff and even security guards at the luxury department store Harrods have held strikes recently. Nurses for Britain’s state health service are threatening their first-ever strike on selected days near Christmas and ambulance drivers have also voted to walk out, for the first time in 30 years. Passport-control officials also announced a strike in December at several U.K. airports.