said in a newspaper interview on Sunday that Italy's political and trade union establishment was trying to block his efforts to "revolutionise" the country.
Renzi, 39, who presents himself as an outsider to Italy's largely discredited political class, said conservative forces would not halt his plans to reform the public administration and change labour rules.
"It's clear that a large part of the ruling class is against us," Renzi, the leader of the centre-left Democratic Party (PD), told Corriere della Sera daily.
As campaigning heats up ahead of elections for the European Parliament this month, Renzi's PD is competing with the overtly anti-establishment 5-Star Movement, which is the second-largest party behind the PD and is gaining ground in opinion polls.
In the interview Renzi took aim at trade unions protesting against his proposals for changes to labour rules, and political critics who say his planned cuts in income tax are not properly funded and will put public finances at risk.
Renzi's broad left-right coalition agreed this week to make it easier for firms to keep temporary workers and apprentices on their books for extended periods without offering them permanent contracts.
The proposals are still before parliament but critics in Renzi's PD and among the trade unions are already up in arms.
They say the plans go in the opposite direction of reforms by former Prime Minister Mario Monti who tried to discourage firms from using temporary contracts which offer workers low pay and few rights.
Renzi dismissed the unions' protests as an unacceptable defence of the status quo.
"The unions can't just carry on as before while Italy suffers," he said. "They can't only worry about pensioners and those who already have a job."
He also dismissed the judgment of a Senate technical committee that his plan to cut income tax by up to 80 euros ($110) per month for many low-income workers was not properly financed and risked pushing up the budget deficit.
Renzi suggested the judgment was a political response to his efforts to abolish the Senate as an elected chamber.
"A revolution has begun, a peaceful revolution but one which the elements of resistance in the system will not be able to stop," the prime minister said.
Despite frequent speculation that fresh elections could be called as early as this autumn, Renzi said his "prediction" was that his government would last until the end of parliament's term in 2018.