The lender’s gross mortgage lending fell to £78bn in 2008 from £102.5bn in 2007.
The CML re-worked the data as if the Lloyds merger, which took place in 2008, had occurred earlier to make a comparison of figures in 2008 and 2007 more meaningful.
Santander retained its position as the second largest lender, having acquired the Abbey brand and having taken over the Alliance & Leicester mortgage book last October, with Nationwide in third place and Barclays in fifth.
Northern Rock also dropped from fourth place to eleventh, with gross mortgage lending of £2.9bn, compared to £29.5bn in 2007.
Gross lending overall totalled £261bn in 2008, 28% lower than its peak of £364bn in 2007.
The CML’s research shows the share of specialist lenders – excluding subsidiaries of UK mortgage banks and building societies – shrunk to 2% in 2008 after accounting for over 7% of gross lending in 2007.