He said he was conscious that he was not running a majority government but promised "a new kind" of coalition government that would become a model for the country.
"You (BJP) may be feeling that this government will go in two or three months, it will not go in two months or one month, but will stay with stability for five years," HD Kumaraswamy said.
In his speech after moving a motion for the vote of confidence, he said "We will work for the people of the state. We are not here to fulfill our personal wishes...I will work for the all round development of the state without any discrimination. I promise a new kind of coalition government that is model for this country."
HD Kumaraswamy said he was not assuming the Chief Minister's post "happily", as he has not got the complete trust of the people.
"I have not become Chief Minister today happily. I have pain. I had placed several issues in front of people during election feeling that they will trust me, but people of the state have not shown trust in me," he said.
I'm not running a majority government, but people have not given majority to any one...they may have given you (BJP) 104, but it is not majority..." HD Kumaraswamy added.
Thanking the Congress for the support, the Chief Minister, while promising not to misuse their trust in him, said he would work towards ensuring good name for the party, and for a "new type" of political development that will begin in Karnataka ahead of 2019 Lok Sabha polls.
People had not given a clear mandate in favour of any party but the BJP believes that the mandate is in its favour.
"I'm still trying to understand what kind of analysis it is," he said.
Promising to continue the popular schemes of Congress government, Mr Kumaraswamy said the government would not only be stable, but would protect the interest of everyone and provide honest and good administration.
"Let's end politics here and look at the interest of the people and development of state," he said.
Trying to find fault with the Governor's decision to invite the BJP to form government first and giving them 15 days time to prove majority, the Chief Minister rejected claims made by BS Yeddyurappa that Congress and JDS MLAs were in captivity.
Recalling his 2006 decision to join hands with BJP, Mr Kumaraswamy said it was a wrong decision that had impacted his father and former Prime Minister HD Deve Gowda's health.
"I had this pain that I have put a black mark on the political philosophy that he (Gowda) stood for all along in over 60 years...he was even hospitalised for 3-4 days as he was pained that I had gone against the secular identity that he stood for."
"In over 60 years of his political life, Deve Gowda was Prime Minister for 10 months, Chief Minister for about 18 months, for three or four years he was minister in Ramakrishna Hegde and S R Bommai governments. In his long political life we have seen power for about 4 or five years only."
Mr Kumaraswamy also conceded that his decision to join hands with Congress was also to wipe out the black mark that he had put on his father's political legacy, by joining hands with BJP in 2006 to form a coalition government.
"I want to tell BJP, if I had not formed government with you then, you would not have seen power in south India, for the BJP's door to power in south India to open, I also have my small role," he said.
Hitting back at BS Yeddyurappa's threat to take to the streets if government does not fulfill its promise of farm loan waiver, Kumaraswamy said the government would not give BJP any chance to go to the streets.
"I need not learn from you about farm loan waiver..I'm not some one who speaks with emotion, I will implement and show...this government is committed to waiving loans of farmers made through cooperative, nationalised and grameena banks," he added.
Later rebutting opposition leader BS Yeddyurappa's speech, Mr Kumaraswamy said it was unbecoming of his age, seniority and experience, and also called BJP's walkout as "escapism."
He said BS Yeddyurappa has spoken like a drama artiste rehearsing for a play in open theatre.
Mr Kumaraswamy alleged that BS Yeddyurappa during the Dharm Singh government had come to him stating that he would quit BJP and had sought a Minister's post.
Targeting the Modi government, he said a false document about him floating a company in Malaysia had been created.
"We need to warn central government also today, they are trying to play keeping Income Tax Department and ED. Do they think they will stay in power for ever? They have started this game of troubling and scaring opponents..let there be any inquiry, I'm ready face it," he added.
Hitting out BS Yeddyurappa's call for bandh if loan waiver is not announced, Mr Kumaraswamy said he has seen several such bandhs.
"If any attempt is made to instigate people, it won't be allowed."