Who is keeping a watch on Pranab Mukherjee?

Finance Minister Pranab Mukherjee had reported a "serious breach of security" in his office in a letter written to Prime Minister Manmohan Singh in September last year, according to a report by the Indian Express.

In his letter, Mukherjee claimed that "planted adhesives" were found in 16 locations including at his office, the offices of his advisor Omita Paul and private secretary Manoj Pant and two conference rooms used by the finance ministry.

Mukherjee clarified that no microphone or recording devices were found in these offices. The paper claimed that the adhesives resembled chewing gum and were planted at crucial places -- three of them were found on Mukherjee's table. The grooves on them may point to a small chip that could have been pulled out later, speculated the Indian Express.

According to the paper, three days before he shot off the letter to the PM, investigators of the Central Board of Direct Taxes had conducted a high-level electronic sweep of his offices and chambers.

The CBDT, which reports to the finance ministry, has been conducting such sweeps regularly to detect any surveillance equipment or electronic bugs that may have been planted in Mukherjee's office.

The paper said that Mukherjee had sought a 'secret inquiry' into the incident. "The PM may consider ordering a secret inquiry into why and how this breach occurred and who is responsible for this action," the Indian Express quoted the letter as saying.

The CBDT's investigation wing is already conducting a hushed probe into the sensitive matter, said the report, adding that security around Mukherjee's offices, chamber and conference rooms has been beefed up.