Former Prime Minister Manmohan Singh on Monday wrote to President Ram Nath Kovind asking him to caution Prime Minister Narendra Modi from using "unwarranted, threatening and intimidating language" that is unbecoming for the country's top post.
The letter was also signed by other senior leaders of the grand old party.
The letter refers to PM Modi's speech in Karnataka on May 6, in which he said: "Congress leaders, please listen carefully, if you cross you limits, then this is Modi. You will pay."
"It is unthinkable that in our democratic polity, the Prime Minister ahead of the government would utter words which are threatening, intimidating in content and a public warning to the leaders of members of the main opposition party, the Congress," the leaders said in a letter to President Ram Nath Kovind.
The Congress leaders said the Prime Minister was not expected to use menacing language even in the course of the election campaign, which amounted to using his powers and privileges as PM to settle personal and political scores.
This could not be the language of the Prime Minister of a constitutionally governed democratic country of 1.3 billion people, said the Congress, calling it unacceptable conduct.