A small number of MPs and peers will face criminal investigations into allegations they misused their expenses.
Scotland Yard said a joint assessment panel of senior detectives and prosecutors had decided full inquiries were necessary.
The police inquiries were expected to focus on politicians accused of deliberately misleading the authorities or claiming “phantom mortgages”.
The investigation will be conducted by officers from the Met’s Economic and Specialist Crime Command, overseen by Temporary Assistant Commissioner Janet Williams. It is understood the joint panel of experts will continue to consider a small number of other individuals.
A Metropolitan Police spokesman said: “After consideration by the joint Metropolitan Police and Crown Prosecution Service assessment panel the Met has decided to launch an investigation into the alleged misuse of expenses by a small number of MPs and peers.”