The caller, identifying herself as the UPA chairperson, called the top lawyer on September 5 and 11, before hearings on the coal block allocation scam.
The caller is learnt to have advised Vahanvati to lie low. But the caller sounded so convincingly like Gandhi that Vahanvati contacted senior Congress leaders.
As the Gandhi was in New York for a medical check-up at the time of the calls, the attorney general suspected something wrong and reported the calls to the home ministry.
A news channel quoted Congress MP Ajay Maken as saying, "It is a very small matter and has nothing to do with the party. Why should the party be dragged into it?"