Six former Volkswagen executives are being charged over their alleged roles in the 2015 emissions scandal, as the company admits liability and is ordered to pay a record $4.3 billion penalty, US officials have said, informs The Guardian.

The men are accused of running a near decade-long conspiracy during their time at the firm and are being charged with conspiracy to defraud the United States, violations of the Clean Air Act, and wire fraud, the US attorney general Loretta Lynch said on Wednesday.

Consequently, the firm has been told to pay a $2.8 billion criminal fine and a further $1.5 billion in a civil settlement, Lynch announced. Volkswagen will also spend three years on probation and an independent monitor will be sent in to “oversee its ethics and compliance program”.

The penalty against the company is the largest ever levied by the US government against an automaker, eclipsing the $1.2 billion fine against Toyota in 2014 over safety issues related to unintended acceleration.

Last month, it was reported that Volkswagen had already agreed to pay $17.5 billion in the US to resolve claims from car owners, as well as regulators.

The settlements and penalties emanate from Volkswagen’s admission in September 2015 that it had installed secret software in vehicles to make them appear cleaner in emissions tests than they actually were. Some, it emerged, were emitting up to 40 times the legally allowable pollution levels.