Pete Doherty has been jailed for 14 weeks for drug use and failing to turn up to probation hearings, throwing his festival plans into jeopardy.
A spokesman for the Babyshambles singer said he will appeal, but if unsuccessful Doherty will miss a number of summer festival dates.
He is due to headline Guernsey Live Music Festival on Sunday 4 May, and is also strongly rumoured for appearances at Glastonbury Festival between 27-29 June.
His band Babyshambles are also due to play at a number of foreign festivals, including Le Printemps De Bourges in France (15-20 April), Rock Am Ring and Rock Im Park in Germany (6-8 June) and Hultzfred in Sweden (12-14 June).
They are also due to play Rock Werchter in Belgium (3-6 July), Les Eurockennes De Belfort in France (4-6 July) and Benicassim in Spain (17-20 July), which would all be cancelled if the full sentence is served.
Judge Davinder Lachar handed Doherty the jail sentence as he attended a West London Magistrates Court today (Tuesday, April 8).
A spokesperson for the court said the singer had been jailed for "breach of time keeping, non-compliance of his order and using different drugs".
He was previously given a suspended jail sentence for possession of drugs and driving illegally and was threatened with up to four months in jail if he broke the law or the terms of his probation.