Kent county council has issued legal proceedings against the home secretary as it warns its services for unaccompanied child migrants are at breaking point for the second time in less than a year.

The authority said it may no longer be able to accept new unaccompanied asylum-seeking children (UASC) within days, and has served a formal letter before action to the Home Office.

Kent has nearly double the number of unaccompanied asylum-seeking children in care the government says is safe to have, the council has said.

The move follows a council announcement last August that it had reached its capacity to care for unaccompanied asylum-seeking children arriving on its shores despite efforts to work with the Home Office and other local authorities.

The council has taken the first steps in legal proceedings to implement a long-term solution aimed at preventing the crisis from occurring again. The proposed judicial review asks the home secretary, Priti Patel, to use existing powers to direct local authorities other than Kent to receive their fair share of unaccompanied asylum-seeking children.

Kent’s director of children’s services has advised the leader of the council that the pace of arrivals and strain on care services is likely to mean he will no longer be able to safely accept any new UASC arrivals before the end of this week.

Border Force will then be asked to place new arrivals directly into other local authorities around the country, as they did for three months last year.

The Kent council leader, Roger Gough, said: “I am deeply saddened that we are now seeing a repeat of the same crisis of nine months ago. While there have been a number of welcome measures from government … we have not seen what is most needed: a robust national transfer scheme [NTS] that prevents port authorities such as Kent coming under unmanageable pressure.

“The Home Office consulted on changes to the NTS in August and September last year and have yet to publish any new proposals or a response to the consultation. The scheme remains voluntary with insufficient incentive for other UK local authorities to transfer UASCs from Kent.

“We must ensure that all UK local authorities with capacity share in the support of these children.”

The Home Office said: “Those who attempt to cheat the system place an unjust burden on the taxpayer and prevent genuine asylum seekers from getting support. This is why the government is bringing forward the new plan for immigration which will allow us to welcome those most in need through safe and legal routes, while preventing abuse of the system.

“We recognise the longstanding role that Kent county council has played in supporting unaccompanied asylum-seeking children and are extremely grateful for their contribution. We continue to encourage more areas to join the NTS and do their part. We have already consulted on how to improve the scheme to make it fairer – the outcome of which will be published very shortly.”

The council said that in the absence of any substantive Home Office response to its proposal by 17 June, it will proceed to issue a claim for judicial review against the home secretary.