A 14-year-old boy has been detained in a Brisbane police watch house for more than a week, according to a formal complaint lodged with authorities.

Murri Court elder Reverend Alexandra Gater has lodged the complaint on behalf of the boy's family, after the child was arrested last week and was still being held today in the watch house.

He has been charged with robbery with violence and stealing offences.

The boy's family was told the child could not be moved because there was insufficient room for him at the Brisbane Youth Detention centre.

The Palaszczuk Government changed laws in 2016 to take 17-year-olds out from adult jails and back into youth detention. ( ABC News: Mark Slade )

"The young boy told his mum that he feared for his safety and he was being bullied by older youth," Reverend Gater said.

"It's inhumane treatment … it's a frightening experience.

"The mother is helpless, that's why she came to me asking for my support."

A spike in the number of children being detained for a week or more at Queensland watch houses, instead of them being transferred to youth detention, is causing an unacceptable level of harm, Brisbane barrister and Youth Advocacy Centre chairman Damien Atkinson has warned.

"You would find at the moment there might be in the order of 20 to 24 young people in watch houses around Queensland, which is totally unacceptable," he said.

He said children were being harmed because they were mixing with adult prisoners and supervised by officers who were not adequately trained to deal with youths.

The State Government said it was normal practice for a young person who had been arrested to spend time in a police watch house before appearing in court and for a short time afterwards.

Mr Atkinson said it was unacceptable for children to be kept in watch houses for too long.

Youth Advocacy chairman Damien Atkinson said 20 to 24 children were being detained in watch houses at any given time. ( ABC News: Tim Swanston )

"There are things being denied to them, simple things like a phone call to their parents," he said.

"In some cases there will be young people in a watch house, it's too crowded and they're moved to another town and that's especially concerning.

"They're deprived of all those connections with their parents, their siblings and the local community."

Full detention centres keep 17-year-olds in adult jails

The Palaszczuk Government passed laws in 2016 to keep 17-year-olds out of adult jails after an ABC Four Corners program highlighted problems in the treatment of young people in prison.

The laws were to be transitioned over 12 months, but earlier this year Child Safety Minister Di Farmer announced the movement of 17-year-olds from adult prisons to youth detention centres would be delayed because the number of young people in detention had risen beyond previous forecasts.

More beds will be added to the Cleveland Youth Detention Centre in Townsville in north Queensland. ( ABC: Brant Cumming )

Mr Atkinson said the changes were welcomed and the current issues should work themselves out in time.

"The challenge is really to use this as an opportunity to say 'let's be more discriminating, let's be more discerning, let's not leave young people in youth detention if they don't need to be'."

In a statement, Ms Farmer said the department was making sure support was being provided to young people in watch houses.

"The number of young people in detention is putting pressure on this process," she said in a statement.

She said construction was about to start to expand capacity at the Cleveland Youth Detention Centre in Townsville by 12 beds so it could accommodate 108 youths.

Work is already underway to add 16 new beds at Brisbane Youth Detention Centre.

"We are also investing in community-based solutions to reduce young people offending and improve community safety," Ms Farmer said.

"Our focus is on preventing young people ever needing to be placed in custody by reducing offending."