The Congress has taken strong objection to Prime Minister Narendra Modi's remarks against its leaders at a poll rally in Karnataka and has written to President Ram Nath Kovind urging him to caution Modi against "unwarranted, threatening and intimidating" language as it does not behove him.

In the letter written on May 13 and released to the media on Monday, Congress leaders, including former Prime Minister Manmohan Singh, referred to Modi's speech in Hubli during the Karnataka Assembly election campaign in which he had warned the Congress against crossing boundaries.

"Hon'ble President may caution the Prime Minister from using such unwarranted, threatening and intimidating language against leaders of the Congress or any other party or person as it does not behove the position of the Prime Minister," the letter said.

In his speech on May 6, Modi had said: "Congress leaders, listen with your ears open, if you cross boundaries, then this is Modi, you will have to pay for it."

The Congress letter said that the words used by Modi were "menacing and intimidating with intent to insult and provoke breach of peace."

It said that all Prime Ministers in the past have maintained immense dignity and decorum "in discharge of public or private functions/actions."

"It is unthinkable that in our democratic polity, the Prime Minister as head of government would utter words which are threatening, intimidating in content and a public warning to the leaders and members of the main opposition party -- Indian National Congress," the letter said.

Apart from Singh, the letter has been signed by senior party leaders Ghulam Nabi Azad, Karan Singh, Mallikarjun Kharge, P. Chidambaram, A.K. Antony, Anand Sharma, Ashok Gehlot, Motilal Vora, Ambika Soni, Kamal Nath, Digvijaya Singh, Ahmed Patel and Mukul Wasnik.

The Congress leaders said that the President as the constitutional head of the union enjoys high duty and obligation to advise and guide the Prime Minister and his Cabinet.

"Admittedly, the Prime Minister is not expected to use menacing language even in the course of election campaign which tantamounts to using his powers and privileges as the Prime Minister to settle personal and political scores," the letter said.

It said that the "threat held out" by Modi to the Congress leadership "deserves to be condemned".

"This cannot be the language of a Prime Minister of a constitutionally governed democratic country of 1.3 billion people. Such discourse whether in public or private is unacceptable conduct."

The party said it would not be cowed down by such threats.