Three Scotland Yard counter-terrorism detectives who investigated the July 7 bombings have been accused of running a sophisticated rent scam.
The trio and three civilians were charged with conspiracy to defraud, the Independent Police Complaints Commission (IPCC) said.
Investigators have been looking into an alleged fraud in which the Metropolitan Police was overcharged for rented flats in Leeds in 2006 and 2007.
The accused officers are Detective Constable Daren Pooley, 40, Detective Sergeant Nevill Caldecourt, 50, and Det Sgt Peter Allbut, 45.
Pooley's wife Nicola, 39, from Sleaford, Lincolnshire, is also charged with conspiracy to defraud along with her sister, Michelle Butler, 49, and brother-in-law Stephen Butler, 58, who live in Spalding, Lincolnshire.
The three officers were also charged with misconduct in public office. The allegations against them include claims they misused their police credit cards.
All six will appear before City of Westminster Magistrates' Court on February 3.
The alleged fraud took place over 18 months from April 2006, an IPCC spokesman said.
He said: "The charges relate to an alleged conspiracy to defraud the Metropolitan Police Service by dishonestly participating in a scheme to overcharge the MPS for flat rentals in Leeds with the intention of making a secret profit thereby and distributing monies so raised among themselves."