Volkswagen is set to plead guilty today to three felony counts in the US relating to the Justice Department's diesel emissions investigation.

In January the carmaker agreed to reforms, new audits and oversight by an independent monitor for three years as part of a plea agreement with U.S. prosecutors announced in January, Reuters reports.

VW admitted to using secret software in vehicles to enable it to beat emissions tests. It is charged with installing the cheat device in 580,000 vehicles in the US.

This came to light in 2015.

Today VW is set to plead guilty to conspiracy to commit fraud, obstruction of justice and entry of goods by false statement charges.

A company lawyer is expected to appear to plead guilty on Volkswagen's behalf.

The US Justice Department in a court filing Monday called Volkswagen's conduct "one of the largest corporate fraud schemes in the history of the United States".

In total, VW has agreed to spend up to $25 billion in the United States to address claims from owners, environmental regulators, states and dealers.