Southwark Council's food hygiene inspectors have found "major non-compliance with statutory obligations" at the authority's own staff canteen.
The staff restaurant, which is operated by the Camden Society, received a rating of 2 ("requires improvement") on scale from 0 to 5.
Inspectors found that whilst food hygiene and safety was "fair", structural compliance with statutory obligations was "poor" and they only had "some" confidence in the canteen's management.
The Scores on the Doors website defines a "poor" rating for structural compliance as meaning "some major non-compliance with statutory obligations – more effort required to prevent fall in standards".
• Figures published earlier this year show that the council spent £580 on mousetraps for the Tooley Street building during January 2013 alone.