Error when I delete a lead

Hi,

I am trying to delete a lead but I am getting a not_authorized error. 
{ ["error"]=> string(14) "not_authorized" ["error_message"]=> string(53) "Not allowed to perform action "delete" on this record" }

the same user when deletes a user it was done perfectly when the same user wants to delete the lead it sent the above one error

please help

Thank you