The Government has issued a statutory direction to Bournemouth, Christchurch and Poole Council forcing it to improve its children's social care services.
Its move comes after a visit from Ofsted in 2020 that found children living in the area were 'not protected effectively'.
A subsequent inspection in December 2021 found the council's children's services were still 'inadequate'.
Inspectors wrote: 'There are still serious and widespread weaknesses in the quality of children's services that leave vulnerable children at risk of harm.
'Specialist services aside, the core business of reducing the risks to children in need of help and protection is yet to have a consistent and effective impact.'
The direction requires the council to take steps to improve its children's social care services, including working with the appointed adviser John Coughlan.
A council spokesperson said: 'While the report identified areas that required improvement, Ofsted also recognised that the key building blocks are in place to drive improvements and highlighted where services are showing progression and working successfully.'
