Prime Minister Singh, had earlier, in an interview with American magazine 'Science' said that the KNPP protest was being funded by foreign NGOs based in the US and Scandinavian countries.
"There is no basis whatsoever for this statement made against my client who is the coordinator of the protest," said Udayakumar's lawyer M.Radhakrishnan.
Claiming that the notice was to hamper Udaykumar's position, the notice read, "your imputation that the said protest is funded by the United States and the Scandinavian countries is an utter falsehood. This imputation of yours may fall within the realm of defamation."
The notice further said that Udaykumar was hurt by PM Singh's statement that "the atomic energy programme has got into difficulties because the NGOs, often funded from the United States and the Scandinavian countries, don't appreciate the need for our country to increase the energy supply."
The notice also said that the statements were being made "with a view to informing the public" that the anti-nuclear protests were being held with the help of foreign hand.
"There is no basis whatsoever for this statement made against my client who is the coordinator of the protest," it said.
"My client hopes that you, as the Prime Minister of India, will immediately make appropriate amends to the statements made against my client, and will not drive him to have recourse to law," said the notice.