New Delhi, Sep 27 (IANS) With Prime Minister Manmohan Singh returning to Delhi Tuesday night, he and Congress president Sonia Gandhi will meet separately with ministers and party leaders Wednesday to defuse a crisis over 2G spectrum allotment involving Finance Minister P. Chidambaram.

Home Minister Chidambaram and Finance Minister Pranab Mukherjee had met Gandhi separately Monday evening to explain their positions over the issue that the opposition has lapped up to demand Chidambaram's ouster.

Congress sources said Gandhi, recuperating after a surgery Aug 4, was making efforts to defuse the situation that has the potential to turn into another crisis for the United Progressive Alliance (UPA) government.

The outcome in the hearing Tuesday of a case filed by Janata Party president Subramanian Swamy against Chidambaram is also considered crucial in the controversy.

Mukherjee reached Kolkatta Tuesday for Duga puja celebrations. He is to return to Delhi Wednesday.

The controversy emerged after an official note sent by the finance ministry surfaced last week saying if the 2G spectrum had been auctioned, it would have led to higher revenue.

Chidambaram was the finance minister then.

The letter was sent by the finance ministry to the Prime Minister's Office(PMO) following a RTI question.

Seizing the opportunity, opposition parties have alleged infighting in the government and demanded the resignation of Chidambaram.

Chidambaram has said he would not comment on the issue till Manmohan Singh returns. Mukherjee met Manmohan Singh Sunday in the US.

On Tuesday night, Law Minister Salman Mhurshid and Minister of State in the Prime Minister's Office V. Narayanasami called on Mukherjee to dicuss the legal implications of the note.

Meanwhile, Coporate Affairs Minister M. Veerappa Moily told reporters here Tuesday that some people "were trying to blackmail the government based on the information received through RTI".

He added: "It is not done. It is unfortunate."