Haringey Borough Council has been made to apologise in court after social workers tried to change the identities of two young children and ban their five older siblings from seeing them.
Senior family division judge Mr Justice Holman refused to allow social workers' plan two weeks ago and ordered that the children be separately represented so that their views could be heard.
The seven children are the offspring of the same Nigerian parents, who are both currently in prison serving sentences for ill treatment of all or some of their children.
Prospective adopters have been found for the two youngest children, and social workers want to change their identities to protect them from their abusive parents.
Social workers wanted to change the children’s surnames and forenames, as well as stopping their brothers and sisters from contacting them or knowing where they are in case their whereabouts was revealed to the parents.
Several years ago the eldest five, now aged from seven to 13, were taken into care by Haringey social services, but no adoption was ever contemplated, and they are with long-time carers in three separate homes.
In May 2012 the two youngest, now aged three and two, were taken into care with plans to have them adopted, but they were granted contact with their siblings.
Mr Justice Holman said that since then there had been contact and “it appears that all the children enjoy and gain support and benefit from that contact”.
The judge said the council’s own social worker admitted that splitting up the children with no contact between the elder five and younger two until they were at least 18 would cause “grief” as well as “pain and loss".
But he said there would be help and support from the professionals and foster carers to help them cope with it.
He added he was “frankly astonished” that he was expected to reach a decision about their futures in only one day, without hearing from the children, but was also “deeply conscious” of the “worrying” delay in the case.
Liberal Democrat councillor Katherine Reece attacked Haringey council for the way it handled the case.
She said: “It is very worrying and disappointing that according to the judge basic mistakes were made in the way this difficult situation was handled by Haringey.
“While there have been some improvements in Children’s Service in Haringey, the Liberal Democrats are repeating our call for an independent inquiry into the service and why serious mistakes keep being made.
“We welcome the appointment of the new Local Safeguarding Children Board Chair. However, we remain vigilant and will keep pushing Labour to make the changes that are needed to keep children in Haringey safe.”
A spokesman for the authority said: “As made clear in our statements to the court, we fully recognise that we did not follow correct procedures in this case and we are taking immediate action to ensure that we improve our processes.
“The best interests of the children involved, who have faced extremely complex and difficult circumstances, have been at the heart of the decisions we have made.
“Our duty of care to those children, and their long term welfare, remains our first priority.”