Ambac, the bond insurer whose finances have been hit by guarantees on billions of dollars of securities linked to risky mortgages, expects growing numbers of lawsuits against the banks that acted as underwriters and managers of these securities.

Last week, a British subsidiary of Ambac Financial filed court papers seeking $1bn in damages from JPMorgan Investment Management. As the investment manager for $1.65bn of assets in the name of Ballantyne, Ambac said JPMorgan had placed the assets in “inappropriate securities”, including risky mortgage-backed securities.