Children as young as 10 have been kept in adult maximum-security watch houses while the government upgrades a Brisbane youth detention centre.

Queensland’s two youth detention centres usually have a capacity of 258 beds, but the upgrades, which began in April last year, caused a loss of 38 beds in the youth detention system.

A staffer at the Office of the Public Guardian says youth are being disadvantaged by the decision and placing children in maximum-security watch houses is a breach of Queensland law.