DWP power to seek information from the Home Office

I have a case where my Lithuanian client clearly has a permanent right to reside as the family member of a qualified person. The DWP provided the information that her estranged husband has a permanent right without me having to throw Kerr around (a first, in my experience - we usually have to get a Tribunal to direct the DWP to get that information), but it will not accept that my client has provided evidence of the marriage. IMO, there is evidence that indicates a marriage (solicitor’s letters, witness statements from grown up kids, same surname - that sort of thing), but we are now waiting for an appeal to be listed for hearing. She cannot access the marriage certificate for very specific reasons, which are totally acceptable and understandable, but the DWP are stating that it will only accept the certificate as evidence. So, my question is:

Can I request that the DWP contacts the Home Office and asks for the information to be sent through RALON (Risk and Liaison Overseas Network)  or something similar? Has anybody had success in doing something like this? Or any advice about other tactics?

The reason I ask is that I have a separate case where the DWP sought information (and received it) about the birth certificates of two of my Romanian clients. This was provided by the RALON officer in Immigration Enforcement and used in an IS/HB living together case. I have a feeling that the DWP will tell me that they were trying to prove fraud in that case which is why they used RALON, and that in the case of this marriage certificate, I can get lost…

Anyway, any thoughts are welcome. Thanks in advance.