Energy Secretary Chris Huhne will learn on Friday whether he will face charges over claims his ex-wife accepted speeding penalty points on his behalf.
Director of Public Prosecutions Keir Starmer is due to make the announcement at 10am, when he will also reveal a decision on Mr Huhne's former spouse Vicky Pryce.
Prosecutors have recently received key emails in the case. The Liberal Democrat minister has repeatedly denied any wrongdoing.
It comes after the Sunday Times recently dropped its challenge to a court ruling ordering evidence to be disclosed.
The evidence is believed to include exchanges between the newspaper's political editor and Mr Huhne's ex-wife.
Lawyers began reviewing the material from Essex Police at the end of January.
An initial evidence file, relating to a March 2003 speeding offence, was delivered to the CPS last July.
Mr Huhne has been warned by Deputy Prime Minister Nick Clegg that it would be a "very serious issue" if he was charged.
Mr Clegg said in a recent interview that he and David Cameron would have to "take a view" if charges were brought against his Liberal Democrat colleague.
He added that the Coalition was determined to uphold the "highest standards of probity" among ministers.
