Ommission of information versus misinformation

Can anyone help with any case law or reprted decisions
I have a client who was advsied to claim carers allowance but not IS by an adviser ( not in the DWP). IS was applied 3 months later but the DWP would not backdate it even though the claimant explained with supporting evidence from the advsier that he did not make a claim earlier as the advsier failed to advise him to claim for IS and the DWP refused to backdate the award. They are quoting Commisioner’s Decision R1 (IS) (T) stating in order for the regulation to apply the claimant must have received some information and it was not sufficient that potentially relveant information was absent. Is there anything we can use to argue that ommission is simialr to misinformation

Thank You