WGM creates ldap entries but dscl doesn't

I can successfully create users and groups in Workgroup manager on my Xserve running 10.5.7 server when bound to my local LDAP directory (127.0.0.1) as the newly created diradmin user but when I try to do the same using dscl in a terminal as the same user I get an error as follows:

/LDAPv3/127.0.0.1/Groups > create . test_group
<main> attribute status: eDSPermissionError
<dscl_cmd> DS Error: -14120 (eDSPermissionError)

I don't wish to use sudo to create the entries as I intend creating users and groups from an external script - but since I can successfully create entries using the same user in WGM, how is it I can't using the same credentials in a terminal?

Any thoughts greatly appreciated...

(I also tried changing the password type of the diradmin from OD to crypt but it doesn't seem to have changed anything...)