Chris Huhne will learn on Friday if he is to face charges over allegations that his ex-wife Vicky Pryce accepted speeding penalty points on his behalf, the Crown Prosecution Service said.
The Lib Dem energy secretary has been accused of avoiding a driving ban in 2003 by getting Pryce, his then wife, to claim she had been at the wheel of the car.
Keir Starmer, the Director of Public Prosecutions, is expected to announce whether Huhne will be charged at 10am.
It is widely believed that if he is charged he may have to step down from the Cabinet and fight the allegations from the back benches.
Huhne's resignation would result in a rare cabinet reshuffle, with senior Lib Dems Jeremy Browne, a Foreign Office minister, or Ed Davey, employment relations minister, tipped for promotion.
The announcement from the Crown Prosecution Service comes after the Sunday Times dropped its its challenge to a court ruling ordering evidence to be disclosed last Friday.
The material is believed to include email exchanges between the broadsheet's political editor Isabel Oakeshott and Pryce.
Huhne has repeatedly denied any wrongdoing.