In reply to a Right to Information (RTI) query filed by a PTI correspondent, it said the exercise would also "disproportionately" divert its resources because the information was not available in a "consolidated" form.
"Collection of information, if any, will require the undertaking of a thorough search of every receipt or communication kept in all the files related to the matter," the PMO said.
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Such an extensive exercise, it said, would "disproportionately divert the resources of this office from the normal discharge of its functions and attract the provision of Section 7 (9) of the RTI Act, 2005."
Under the Section, "information shall ordinarily be provided in the form in which it is sought unless it would disproportionately divert the resources of the public authority or would be detrimental to the safety or preservation of the record in question."
The PMO was asked to give details of permissions sought by companies, trusts and individuals for using the prime minister's photographs with copies of communications accepting or denying such requests.
In response to another query, the PMO said it had no record of permission sought by Reliance Jio and Paytm for the use of Modi's pictures in advertisements.
"The information sought does not form part of the records held by this office," it said.
In September last year, Reliance Jio had in full-page newspaper advertisements dedicated the Reliance Jio 4G service to the Modi government's flagship Digital India project.
The advertisements were published with a photograph of the prime minister, triggering a political controversy. Delhi chief minister Arvind Kejriwal had tweeted: "PM of India openly endorses Reliance product."
After the government announced demonetisation of currency notes on November 8, Paytm, an Indian digital wallet, issued an advertisement, with the PM's photograph, welcoming the move as it boosted the use of online payments.
The Department of Consumer Affairs had sent notices to both the companies under the Emblems and Names (Prevention of Improper Use) Act of 1950, which bars the commercial use of the prime minister's name and picture.
In March, the government informed Parliament that Reliance Jio and Paytm had apologised for their "inadvertent mistake" in using Modi's photograph in their advertisements without permission.
Section 3 of the Emblems and Names (Prevention of Improper Use) Act of 1950 stipulates that "no person shall use or continue to use" any name or emblem for the purpose of any trade, business, calling or profession without the permission of the central government.
The law provides that "any person who contravenes the provisions of the Section shall be punishable with a fine, which may exceed to Rs 500".