The Security Bureau on Thursday rejected criticism of the cost of a HK$5.5 billion rebuild of the Lai Chi Kok Reception Centre, saying it's adopted an attitude of "fitness for purpose and no frills" in coming up with the design for the remand prison.

The bureau made the comments after criticism from some members of the Legislative Council's public works subcommittee, who questioned the cost of the project and the facilities, including extended areas for medical and religious purposes.

Officials said the Correctional Services Department was "committed to providing a secure, safe, humane, decent and healthy custodial environment for persons in custody" and needed to "solve the problem of aging facilities and overcrowding of the custodial environment" at Lai Chi Kok.

Most of those held at the prison are on remand or awaiting trial, and the bureau said the "aging facilities and insufficient support infrastructure ... not only affects the custodial environment but also the rehabilitation" of prisoners.

On the question of medical facilities, the bureau said this would not only ensure that sick inmates receive medical treatment, but "also significantly reduce the security risks posed to the community associated with transferring [people in custody] to and from public hospitals or clinics."

Dental treatment within the institution is different from that provided in the public dental clinics in the community, it added. "The treatment in the institution is provided by dentists from the Department of Health who visit periodically for consultations (typically one to two times per month)."

It said the provision of religious services was designed to support prisoners "from the moral and spiritual perspectives".

"The design principles of 'fitness for purpose and no frills' have been adopted in the redevelopment project, and the concepts of standardisation and simplification in the design and construction arrangements of the project have been applied as far as possible," it added.

The bureau said the costs were comparable to the redevelopment of the Tai Lam Centre for Women in 2011, adjusted for the change in prices since then.

The matter will next go to the Legco Finance Committee after the public works subcommittee voted unanimously to allow it to proceed.