The arrangements for England and Wales will apply to all applications received on or after 16 April 2012.
Arrangements in Scotland are unchanged.
Michael Webber, head of legal services for Clydesdale and Yorkshire Banks, said: “Clydesdale and Yorkshire Banks see CQS as a positive development and is encouraging further membership of the scheme.”
Desmond Hudson, chief executive of the Law Society, said: “Lenders make their own decisions about their panels, so we regard Clydesdale and Yorkshire Banks’ decision to make CQS a requirement for panel membership as further demonstration that CQS is a trusted community of skilled practitioners.
“Not only is it an assurance of high standards in conveyancing for lenders, but by showing its commitment to CQS, they are also putting customers’ interests first by maintaining a wide panel of trusted firms.”
