Men from Calderdale, Kirklees and Wakefield who need NHS care will use the new facilities.

It will provide assessment, treatment and rehabilitation for people with severe mental health problems who require care under low secure conditions and who may have been in contact with the criminal justice system.

The Bretton Centre – the result of an £8m investment to convert four vacant buildings on the Fieldhead site, in Ouchthorpe Lane – has been in development since 2006.

It has been created after services previously provided at the Castle Hill unit on the St Luke's site in Huddersfield were relocated. The centre will provide an expanded service and extends the provision to include the Wakefield district for the first time.

Steven Michael, chief executive of South West Yorkshire Mental Health NHS Trust, said: "I'm delighted we have opened this new facility, which not only provides an enhanced service to the people of Calderdale and Kirklees but also extends provision to the Wakefield district, enabling more local people to receive NHS treatment closer to home.

"The new facilities will help us to provide care that meets individual needs from admission through to discharge."

The clinical team has also been expanded and now includes an additional consultant psychiatrist; a larger psychology team; more than double the staff in the occupational team; a dedicated drug and alcohol worker; physiotherapy input; dietician input and over 30 additional nurses.

The service will also benefit from a new therapy and recreation centre, the Oasis Centre, which has been designed and planned around the needs of people who use trust services and is due to open next month.

It will include a music studio, a fully equipped gymnasium, art and crafts room, function room, rehabilitation kitchen, IT suite, sports/recreation hall and a coffee shop. Service users, their families, commissioners, GPs, MPs and NHS staff were invited to tour the new buildings prior to the opening.

Joyce Catterick, trust chair, said: "The Bretton Centre has transformed existing space into a high quality, bright and pleasant environment for patients and staff as well as incorporating the very latest in safety security equipment.

"People who use the service have been involved in many of the decisions to ensure we have designed a facility that fully meets their needs. The whole service highlights how additional investment brings real benefit to local people who need NHS care."

The areas within the Bretton Centre are the Sandal Unit, a six-bed admission and assessment unit; the Thornhill Unit, a 15- bed continuing care / treatment unit; the Almondbury Unit, a 10-bed rehabilitation and recovery unit offering care for those needing long-term help; and the six-bed Ryburn Unit, which offers care prior to a patient being discharged from hospital.