Inspectors visiting Portsmouth Council last month rated children's social care provision at the council as "good" overall, marking progress on 2014 when it was rated "requires improvement".
"Despite increasing demand, leaders have made good progress in establishing a resilient and sustainable service," Ofsted's inspection report states.
"The senior leadership team articulate a clear, shared vision and set of values. They are ambitious and have an accurate and realistic understanding of the strengths and areas for development of the service. They use this knowledge well to actively improve services.
"Effective planning has led to a more secure and stable workforce, and most workers have manageable caseloads. Strong political and corporate support for children's services ensures that children's needs are prioritised."
Inspectors said that direct work with children and families is a key strength of the service, with social workers supported to deliver "meaningful interventions to sustain positive change and safe long-term outcomes for children".
The report adds that the senior leadership team has worked "resolutely" to create a learning culture that is responsive to change, created a sustainable quality assurance system that supports continual service improvement.
"The rigour applied to quality assurance is impressive and ensures that agreed standards are met and that outcomes for children improve," the report states.
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However, inspectors did raise some concerns. They said that child protection plans are not clear enough about what needs to be achieved, the specific actions required, or the timescales for completion.
Meanwhile, although pre-proceedings were found to be used appropriately when risks escalate, or when children's situations do not improve, a small minority of children were found to remain subject to pre-proceedings for too long.
Alison Jeffery, director of children's service at Portsmouth Council said: "The report is a credit to our social workers and early help staff, and what they achieve for the city's young people. I know just how hard they work and it is fantastic to see the quality of that work recognised by Ofsted.
"They put children and their welfare at the forefront of everything they do. I'd like to thank all our staff for the commitment and dedication they show every day. We are determined to build on this and keep improving."