A top federal prosecutor in New York will on Thursday declare another front in the war on Wall Street fraud, focusing new resources on civil litigation to complement existing criminal actions.

The move by Preet Bharara, US attorney for the southern district of New York, comes amid criticism of the relatively small number of criminal prosecutions brought after the financial crisis. The district has mounted high-profile prosecutions after previous crises.

"Not every case is a criminal case," Mr Bharara told the Financial Times. "It's important for us that we deploy all the tools we have, even in cases where a criminal prosecution is not appropriate."

Mr Bharara will announce the appointment of Heidi Wendel, a former New York state deputy attorney-general, to head a six-strong unit focused on taking civil enforcement action against fraud. Her remit covers "every single type of fraud", including complex financial misconduct, mortgage deals, abuse of the government's troubled asset relief programme and healthcare scams, Mr Bharara said.