The Care Quality Commission (CQC) has issued two warnings demanding "immediate improvements" at Basildon and Thurrock University Hospitals NHS Foundation Trust.
The action comes after an unannounced inspection at Basildon University Hospital on November 3rd that was "prompted by a number of serious incidents involving the care of children at the trust".
During the visit to the acute hospital, inspectors identified a number of serious concerns.
In addition to the warnings, the CQC also told the trust it must commission an independent investigation into its paediatric services.
The hospital was earlier warned over standards in accident and emergency department and adult wards, in July.
What our inspectors found at the trust on November 3rd was completely unacceptable.
"We have taken this action to assist in driving through improvements which have a positive impact on the people being cared for at the hospital.
"It is imperative that the trust now ensures it makes changes which are sustainable, embedded and maintained for the future.”