"Fadnavis is a good person (but) he lacks the administrative skills and acumen to run a government. He cannot face and tackle new challenges," he told reporters here.
Rane said the new CM and his ministerial team is a "weak Cabinet" which is not capable of fulfilling the aspirations of the people.
Rane, who had headed Revenue and Industry portfolios in separate stints in the erstwhile Democratic Front government, also criticised Fadnavis for his statement that a separate Vidarbha state would be formed at an "appropriate time".
Fadnavis had said in Nagpur yesterday that his party principally stands in favour of smaller states. "But the Centre will decide when to carve out a separate state. It will be done at an appropriate time. But we want to do it amicably and not like Telangana," he had said.
As an MLA from Nagpur, Fadnavis has been a strong votary of a separate Vidarbha.
Rane also lashed out at Fadnavis for "reneging" on BJP's pre-poll promise to shut down all toll plazas in Maharashtra after coming to power.
He also attacked Fadnavis for his statement that industrialists in Mihan project in Nagpur would get direct electricity supply.
"What happens to the state electricity board which gives subsidies of Rs 10,000 crore to farmers from funds generated from industrial tariffs," Rane questionned.
"Within six months, people would realise that the previous Congress government was better," he said.
In the recent elections, Rane, known as a strongman from Konkan region, had lost to a Shiv Sena candidate from his pocket-borough of Kudal in Sindhudurg district.