The gloves are off between Union home minister P Chidambaram and finance minister Pranab Mukherjee. Chidambaram’s political image suffered a dent on Wednesday when Mukherjee’s secret note to the prime minister’s office (PMO) questioning his role in the 2G spectrum allocation scam became public.

The Congress is worried about the adverse political fallout of the open war between two of its senior-most ministers. Political circles are speaking in hushed voices about how an astute Mukherjee took revenge on Chidambaram for the alleged wiretaps that were installed in the offices of the finance ministry earlier this year.

Though Mukherjee made attempts to brush aside the controversy after initially raising a stink with the prime minister, the simmering differences between him and Chidambaram is an open secret. A section within the Congress acknowledges that Chidambaram has been cornered by his rivals within the establishment.

An official said the PMO released the letter questioning Chidambaram’s role in the 2G scam under the Right To Information (RTI) Act in response to a query by a ‘disinterested person’. The manner in which Mukherjee on Thursday in the US lauded the RTI Act only buttresses the feeling. The finance minister acknowledged the note, but refused to comment on the issue as the matter was sub judice.

Sources said the PMO could have avoided releasing the letter citing confidentiality, but it did not. “It appears that someone in the PMO is an interested party as well as involved in the fight,” the source said.

Bolstered by Mukherjee’s refusal to bail out his colleague, the opposition is baying for Chidambaram’s blood and demanding his resignation. “His position would be untenable if the Supreme Court decides that there should be an inquiry against him too,” said a senior Congress leader.

Chidambaram has kept quiet on the issue instead of resorting to his usual aggressive posturing. “The prime minister called me last night from Frankfurt. The finance minister called me from Washington. I have assured the prime minister that I shall not make any public statement on the subject till he returns to India,” Chidambaram said in a carefully-worded statement.

Political insiders say Chidambaram’s stoic silence could pave the way for a truce with Mukherjee once Manmohan Singh returns from the US. But developments in the Supreme Court can change the situation completely. Chidambaram and Mukherjee have a lot to explain.