Local authorities will only be classed as "outstanding" for adoption if they place children within 12 months, under new plans to speed up the process.
Inspectors Ofsted said delays in adoption could impact children's health, adding that the younger a child is placed with a new family, the better they do.
The watchdog's deputy chief inspector said the plans were aimed at "raising our expectations for ur children."
"It is essential that children in care, often the most vulnerable, get the very best support to have a happy, stable and fulfilling childhood. That is why we want to raise standards further and focus on what real difference is being made to children's lives.
"Our scrutiny of delays in the adoption process will help focus and bring forward a smooth and quicker adoption process. The earlier children are identified for adoption and placed with a family the better the chances that adoption will be successful."
Ofsted also plan to examine whether children are adopted with their brothers or sisters when possible, and if adoption has not been considered as a last resort for children in care.
"Inspection will have a key focus on how quickly adoption agencies place children when adoption is in their best interest," a spokesperson said.
The British Association of Social Workers (BASW) warned that Ofsted should focus on what was best for children "rather than rushing to adhere to inappropriate adoption deadlines."
"We want to see Ofsted highlighting good practice, so that it can be shared between local authorities, rather than fostering a negative culture of competition.
"Inspections should also be factoring in adoption breakdown, rather than rushing to adhere to inappropriate adoption deadlines, the future happiness of the child should come first.
"Resources are also a key factor, we want inspections to appreciate the context of the environment that social workers are working in, i.e., staff shortages, number of cases, how many are allocated, workload management, support to staff through supervision, professional development, etc.
"Making judgements based on whether a local authority has hit the 12 month target should not become the obsession above all else," said the BASW's Nushra Mansuri.
She added: "We hope that Ofsted will also consider occasions when adoption delays might actually be explained by delays in the family courts, for example, when a birth parent opposes the adoption. It is not simply a matter of looking at the performance of local authorities in isolation."
Children's Minister Tim Loughton said: "I welcome this change to the adoption inspection arrangements. Finding stable placements for vulnerable looked-after children must be a top priority for local authorities, but there is currently too much inconsistency and variation.
"I want to see radical improvements to ensure that all children who would benefit from adoption are placed as quickly as possible to make sure they get the start in life they deserve."
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