A dossier of failures by and criticisms of the G4S and Serco is being handed to Scotland Yard by justice campaigners who are demanding that the pair of scandal-hit outsourcing giants be banned from public contracts in the UK.
The Howard League for Penal Reform compiled the report called "Corporate Crime? A dossier on the failure of privatisation in the criminal justice system".
It features an extensive list of recent scandals surrounding the two firms and their public work, including the overcharging of taxpayers for the electronic tagging of offenders and a list of concerns raised by prisons inspectors.
Both G4S and Serco are already under investigation by the Serious Fraud Office (SFO) over their Ministry of Justice tagging contracts in which it was discovered that the public purse was invoiced for work never carried out, such as because the offender was dead.
"We are asking the Metropolitan Police and City of London Police to use their resources and expertise to help the SFO with its complex investigation into possible widespread criminality by companies profiting from public money when they deliver justice services," said Frances Crook, chief executive of the Howard League.
"The dossier compiled by the Howard League is a litany of failure by private companies.
"The delivery of justice is one of the most precious public services and we must, as a nation, adhere to the highest standards of probity.
"The possibility of systematic fraud of the public purse on a massive scale by profiting companies diminishes justice."
A recent poll by Survation on behalf of public services campaign group We Own It found that 80% of people thought Serco should be banned from government contracts.
And a report by parliament's Public Accounts Committee (PAC) said the government must "get its house in order" over outsourcing.
It said just a handful of large businesses were controlling lots of public services because SMEs were being crowded out from the procurement process by its unnecessary complexity, bureaucracy and high cost.
"Private provision of public services has become big business, with half of all public spending on goods and services going to private providers of contracted-out services," said Margaret Hodge, chairwoman of the PAC.
"We believe government needs to urgently get its house in order so that this expenditure is properly open to public scrutiny, and that measures are put in place which will improve services and secure a better deal for the taxpayer."
She added: "There is a lack of transparency and openness around the government's contracts with private providers, with 'commercial confidentiality' frequently invoked as an excuse to withhold information."