Mumbai: Chief Minister Devendra Fadnavis made the announcement in the Lower House and described Waddetiwar as a grassroot leader who has risen from the ranks.
"I wish him good luck as a strong opposition leader is required to keep a watch on the government. We need quality and constructive opposition," he said.
Beginning his political career from the National Students' Union of India (NSUI), a student wing of the Congress, Waddetiwar later joined the Shiv Sena and was its MLC from 1998 to 2004.
In 2004, he was elected to the state Assembly for the first time from Chimur seat on Sena's ticket.
But, in 2005, he came back to the Congress later won the by-election from Chimur on its ticket He then served as a minister in the Congress-NCP government and in 2014, he got elected as an MLA from Brahmapuri seat.
Taking potshots at the opposition over its criticism of the government to appoint Radhakrishna Vikhe Patil, who recently quit the Congress and the post of LoP, as a state cabinet minister, Fadnavis dubbed NCP leader Chhagan Bhujbal as the "father of defections".
In early 1990s, Bhujbal along with a group of MLAs had quit the Shiv Sena and joined the Congress.
"I am not aware of the history prior to that since I was quite young," the 48-year-old chief minister said.
"Waddetiwar hails from Chandrapur, just like me and (state BJP minister) Sudhir Mungantiwar. Waddetiwar has been promoted in the Congress because he was instrumental in getting his party lone Chandrapur seat in the state (in the Lok Sabha polls this year)," Fadnavis said.
NCP leader Ajit Pawar said Waddetiwar would get to play a "20-20 match", as only seven working days of the legislature were left. This is the last session of the state legislature before the state goes to polls in September-October.
Later, BJP member Eknath Khadse took potshots at Vikhe Patil, saying the latter has been lucky to be the LoP and become no.3 in the state cabinet during the same term.
"I will not continue Vikhe Patil's legacy," Khadse said, referring to speculations earlier that he may quit the BJP. Khadse was the LoP during the earlier Congress-NCP government in the state.
After he resigned from the Fadnavis cabinet two years ago following corruption allegations in a land deal, there were speculations that he may quit the BJP. But, Khadse always denied such rumours.
Khadse said Waddetiwar should be thankful to Vikhe Patil for his elevation as the LoP.
Later, Waddetiwar said in the House that though he had less time to function as the leader of opposition, he would strive to make maximum use of it to highlight people's issues.
"I will make use of whatever responsibility has been thrust on me," he said. Ganpatrao Deshmukh (PWP) and Eknath Shinde (Shiv Sena) also spoken on the occasion.