Report generates incorrect SQL however under "Super User" is correct

We have a report that lists categories of vehicles depending on different criteria. The report is a custom one and is derived from "Contacts" under the "Constituent Report (Detail)" template.

If I run the report as a non "Super User" it appends this piece of SQL to the generated select clause:

AND `contact_civireport`.`is_deleted` != 1 AND `relationship_civireport`.`contact_id_a` IN (SELECT `id` FROM `civicrm_contact` WHERE is_deleted != 1) AND `relationship_civireport`.`contact_id_b` IN (SELECT `id` FROM `civicrm_contact` WHERE is_deleted != 1)

which in turn generates this error:

Database Error Code: Unknown column 'relationship_civireport.contact_id_a' in 'IN/ALL/ANY subquery', 1054.

Running the report as a "Super User" the generated SQL does not have these lines and runs to completion.

I have checked all the database tables and can see nothing in there which would suggest a reason for these additonal lines to be added.

I have had an open question on the forum but no responses to it : https://civicrm.stackexchange.com/questions/18725/error-occurs-unknown-column-relationship-civireport-contact-id-a-however-not