Recently Ken Follett, husband of Barbara Follett MP told Andy Marr on BBC TV that "I actually subsidise [her office] to the tune of every year at least a hundred thousand pounds a year". Under the rules any financial or material support above £1000 from a single source should be registered with the Electoral Commission and the Register of Members' Interests. However, Barbara Follett has done neither.
She has registered that she has remunerated employment as a communications consultant for her husband. However, according to the Parliamentary rules anything "from which the Member receives any financial or material benefit in support of his or her role as a Member of Parliament" should be registered as sponsorship.
The Huntsman has much more detail here.
Update 17:20: A statement has been issued by Follett.