The former Game Of Thrones star is not happy with the latest task's rules and his disobedience has meant the housemates' hot water has been taken away.
In scenes set to air on the Channel 5 show tonight, the 68-year-old is seen explaining his decision not to wear the compulsory superhero costume to Big Brother.
"I’m sure that Lycra looks good on some people. It certainly doesn’t look good on me… that’s not going to happen," James C commented in the Diary Room.
The stars were then gathered and the news is revealed to them, while the actor keeps his head down.
Celebrity Big Brother 2017: James Cosmo has refused to wear a superhero costume
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Lycra certainly doesn’t look good on me…
"Although James C is still taking part in the Big Brother hero training camp, he has refused to wear his costume.
"As this is a breach of the rules, there must be consequences. So there will be no hot water until further notice," they were informed by bosses.
Meanwhile, during the upcoming instalment, some of the contestants appear to have won a challenge that allows them to demand the others bring them food, according to The Sun.
Celebrity Big Brother 2017: James C's housemates did not look impressed
Celebrity Big Brother 2017: James Cosmo said he didn't look good in Lycra
James C's shock decision comes after the public saved him, Speidi and Jedward from eviction, while ex Strictly Come Dancing professional James got the boot.
Celebrity Big Brother continues tonight at 9pm on Channel 5.