The Care Quality Commission visited the hospital in June and said "people did not always experience care, treatment and support that met their needs".
It follows a similarly damning report in May when it was told to raise quality and safety to higher standards.
The hospital's director of nursing Clare Culpin said "action plans" were in place to deal with the problems.
The latest inspection found the hospital had made some significant improvements since May relating to cleanliness and infection control, stating that standards were now being met in those areas.
However, it found there were failings around the care and welfare of patients.
In some departments inspectors discovered that daily care plans were brief and did not contain important patient information.
The report added that in some cases, there were very few or no instructions for staff to follow as to how the needs of people were to be met.
Inspectors also found issues with staffing - particularly at weekends - and that "not enough children were receiving the specialist attention that they required" in Accident & Emergency.
The CQC said it had since taken "enforcement action" on the hospital trust and outlined a number of improvements it should make.
Ms Culpin said: "Kettering General Hospital is absolutely committed to improving safety and the patient's experience of care and these inspections enable them to focus even greater attention on any areas of concern."
She added the trust was acting on all issues raised by inspectors and had "systematic action plans" in place to tackle the problems.
Kettering General Hospital is still failing to provide a good standard of patient care, inspectors have said.