The Welsh Government has announced that it will set up a ministerial board with an independent chair to assist Pembrokeshire council to address deficiencies in its child protection procedures, structures and governance.
Mrs Thomas made a statement on Pembrokeshire County Council following concerns over child protection on 20 September 2011.
The minister stressed that the failure of the council to protect children had resulted in many children being harmed.
Care and Social Services Inspectorate Wales (CSSIW) and Estyn started a joint inquiry into the council following 25 cases of alleged professional abuse between 2007 and 2011, plus one additional case that has subsequently been reported.
Some of these cases concerned David Thorley, head teacher at a Pembrokeshire primary school, who was convicted and jailed in May 2009 of nine sex assaults against children.
In her statement, Gwenda Thomas AM said that responsibility for these failings rested solely with the Council.
She added: "The responsibility for putting it right rests with them also but we do not believe that the Council can achieve this on their own."
Mrs Thomas said that she had received assurances from the leader of the council that they would co-operate fully with the investigation.