The increase builds on the 12% increase, by number of cases and value, it reported in August.
Quarter three figures also showed ongoing growth with the value of mortgages up 22.5% on the previous three months and case numbers up 19%.
The results also showed a 71% increase in mortgage completions over the same period in 2012
Mortgage protection and life assurance sales have shown continued strong trends. Quarter three completions were up 18% on the previous three months and 35% over the same period in 2012.
Richard Adams, managing director of Stonebridge Group, said: “After a steady start to 2013 our figures since March have grown significantly meaning quarter three was by far the best three-month period we have enjoyed for a number of years.
“While the improvement over quarter two this year was very pleasing it is our year-on-year results which show just how far the UK mortgage market has come in a relatively short space of time.
“In terms of mortgages completed by value we are almost double the same period in 2012 and nearly three-quarters up in terms of numbers of cases.”
Stonebridge put the increasing business levels down to a number of factors notably an ongoing increase in the number of advisers within the business and an improvement in overall productivity levels.
Stonebridge Mortgage Solutions has close to 200 directly authorised advisers and is a member of the Nouveau Mortgage Club.
