Any ideas on the following scenario:

Couple claiming Income Support. Husband on Incapacity benefit. Wife wishes to relinquish Carer's Allowance for lookng after adult son in order to enable him to receive Severe Disability Premium. Is concenerned about loosing NI credits.Wife is also unfit to work but currently has no other claims that will enable her to maintain her credits.
Could she claim contribution based ESA without it affecting the husbands joint claim for Income Support or would DWP expect the couple to reclaim ESA as a couple? (husband to take over the caring role and wants to establish an underlying entilment to Carer's Allowance)

Any ideas, thanks.

I think I have an answer to my own question.The husband now receives an appropriate level of DLA care. As such his wife will be able to formally transfer her caring role to him, and she claims Home Responsibilities Protection thereby protecting her basic state pension.