GMAC-RFC, part of the financial services arm of General Motors, has sold a portfolio of mortgages worth £135 million to Amber Homes Loans, part of the Skipton Building Society.
The deal is the seventh that GMAC has struck with Amber and its 53rd in total.
It brings the total value of portfolio disposals since 2000 to £ 8.6 billion. GMAC, Britain's 10th largest mortgage lender, said more and more building societies, mortgage and investment banks were becoming active in the market.
European investors, particularly, are using portfolio trades as a way into the buoyant British housing sector.
"This latest sale both confirms our position as the UK's number one trader of mortgage portfolios and confirms the effectiveness of our create and trade strategy," said Craig Beresford, head of asset sales.
"We fully intend to expand our trading programme as we both increase our production volumes and experience increased demand from both traditional and new buyers."
Mark Smitheringale of Amber said the trading of mortgage assets had become an important part of the company's business.
"It has enabled Amber to achieve business growth in a controlled and structured manner," he added.