Leader of the council Paul Carter has written to London mayor Boris Johnson calling for a summit of London councils to discuss how they can better work together to find foster carers and residential children’s home placements in the capital.
There are currently 1,267 looked-after children placed with independent fostering agencies and privately registered children's homes in Kent by other local authorities.
Carter has also written to children's commissioner for England Maggie Atkinson to highlight the issue.
“Being taken into care is probably the most traumatic thing that can happen to a child,” Carter said.
“Children in care deserve a better deal and all councils must work much harder to provide placements that enable them to remain in their schools and with their friends, unless there is a threat to their safety.
“This will minimise disruption in their lives and protect the wellbeing of some of our most vulnerable children."
The council has said that supporting its 1,790 looked-after children, including 181 unaccompanied asylum-seeking children, as well as the 1,267 looked-after children placed by other local authorities, is placing massive pressures on children's social services, schools, police and health services.
There are 63 privately registered children's homes and 32 independent fostering providers in Kent, catering for 803 children placed by London councils and other authorities including Manchester.
Carter and Jenny Whittle, Kent’s cabinet member for specialist children’s services, met with children's minister Tim Loughton to call for legislation that would place a statutory obligation for local authorities to place children no more than 15 miles away from their home or school, unless in exceptional circumstances.
The legislation proposed by Kent would also require all councils to provide an annual statement to their local safeguarding children board detailing how many children are placed outside their local authority boundary and what safeguards have been put in place to protect these children from harm.
It would also require all 32 London councils to jointly commission fostering placements and residential children home placements in London.
Carter added: "Following the recent conviction of nine members of a sex-grooming network in Rochdale, all councils must make sure they can properly safeguard teenagers placed in residential children’s homes, particularly those placed many miles from home, which increases their sense of vulnerability.”