Vicky Pryce is facing jail after being found guilty of perverting the course of justice over ex-husband Chris Huhne's speeding points.
The 60-year-old economist was open-mouthed in shock as the jury announced their unanimous guilty verdict.
Former energy secretary Huhne pleaded guilty last month to perverting the course of justice by passing his points to Pryce in 2003, ending his political career.
Speaking outside the courtroom, her solicitor said she was "naturally very disappointed" at the verdict, and thanked her friends and family for standing by her.
Judge Mr Justice Sweeney granted Pryce bail until sentencing, a date for which has not been set, when he will also sentence Huhne.
He told the economist, as he had told Huhne, to be under no illusion of what sentence to expect.
"Obviously Ms Pryce was present when I indicated to Mr Huhne the inevitable consequences of a conviction for an offence of this sort.
"She must be under no illusions that my granting of bail indicates any watering down of that provisional approach."
He thanked the jury for discharging their task "assiduously" in a case which could not have been easy.
Assistant Chief Constable Gary Beautridge, from the Kent and Essex Serious Crime Directorate, which investigated the offence, said: "The conviction of Chris Huhne and Vicky Pryce has been achieved through the thorough and steadfast investigation conducted by officers and specialist staff at Essex and Kent Police.
"Perverting the course of justice is a serious offence.
"We hope this conviction serves as a timely reminder to motorists who try and avoid driving bans by 'giving' their points to others.
"This practice is not only unlawful, but has life changing consequences for those who get caught flouting the rules."