Congress veteran Amarinder Singh resigned as chief minister of Punjab on Saturday, declaring he feels "humiliated" and that he won't accept state Congress president Navjot Singh Sidhu as the next CM or the party face in the Assembly polls.

The development came amid a power tussle that polarised the ruling party in the state headed for elections in just about four months. Sidhu was made the state Congress chief earlier this year despite opposition by Amarinder Singh.

"I feel humiliated," Amarinder Singh told reporters outside the Punjab Raj Bhawan after submitting his resignation to Governor Banwarilal Purohit. "I have resigned, let them make anyone (next CM)," he further said.

However, in another interaction with the media, the Congress leader said he won't accept Navjot Singh Sidhu as the Punjab chief minister, describing him as "a total disaster".

He said he will never agree to Navjot Singh Sidhu as the next chief minister. "When he was a minister (in Amarinder cabinet), he could not even run one ministry, now can he run entire Punjab? I know that man has no capability at all," Singh said.

If Sidhu was made the face of the Congress for the Punjab polls, Singh said. he would oppose him "tooth and nail".

Earlier in the day after submitting his resignation, when asked about his next course of action, Singh told reporters, "There is always an option and I will use that option when time comes."

"I have been in politics for the past 52 years and I have been a chief minister for nine-and-a-half years. I will talk to my colleagues, supporters," he said.

He submitted his resignation along with that of his council of ministers, his media adviser said. The resignation has been accepted by the Governor.

Singh's resignation came hours before a crucial meeting of the Congress Legislature Party (CLP) on Saturday evening, pre-empting what was widely being seen as a move to remove him from the CM's post.

In the meeting, Punjab Congress MLAs authorised party's national president Sonia Gandhi to pick a new CLP leader and in a unanimously passed resolution praised Amarinder's contribution for Punjab and the Congress.

"I spoke to the Congress president in the morning and I told her that I am resigning today," Amarinder Singh told reporters. "They called the MLAs to Delhi twice and now convened a CLP here in Chandigarh today," he said.

"I think if there is an element of doubt on me that I could not run (the government) or if there was something else, I feel humiliated the way things have happened," he said.

To a question on joining any other party, he said, "Whatever you have to say, you can say. I can only tell you that I have been a chief minister from the Congress. And I am in the Congress and I will consult my colleagues and then we will decide the future course of politics."

"I have only resigned for myself," he said.

"I hereby tender my resignation as the chief minister, and that of my council of ministers," the one-line resignation letter said.

In another interaction with the media later, Amarinder Singh said he had already told Sonia Gandhi during his meeting with her a few weeks back that he should be relieved of the charge. "I had told her that you relieve me of this charge because I cannot work in this way where Mr Sidhu is pulling right and I am pulling left. In that meeting, Congress general secretary (Harish) Rawat was also present. Soniaji then said no I want you to carry on," said Singh.

The Congress leader said he performed his duty to the best of his ability. "I have been in politics for 52 years, so I don't care about these things, I am in politics and I will remain in politics," he said when asked about the circumstances in which he had to resign.

"In politics, options are always there, they are never closed. I can tell you one thing, I am not going to leave it like this," he said. Politics is a very fast moving game, he said replying to another question.

Singh was accompanied by his wife and MP Preneet Kaur and son Raninder Singh when he submitted his resignation to Governor Banwarilal Purohit. MPs Gurjeet Singh Aujla and Ravneet Singh Bittu, AG Atul Nanda and Chief Principal Secretary to CM Suresh Kumar were also present.

"I am proud to accompany my father to Raj Bhawan when he submits his resignation as CM of Punjab and leads us as head of our family into a new beginning," Raninder Singh said in a tweet earlier.