Italian Prime Minister Giuseppe Conte Thursday criticised regional chiefs for defying the government and lifting lockdown measures early, saying it risked undoing efforts to prevent a second Coronavirus wave.
He also rebutted opposition accusations that he was robbing Italians of their constitutional rights.
"Initiatives involving less restrictive measures are contrary to national rules and are therefore to all intents and purposes illegitimate," Conte told parliament.
Regions south of Rome have suffered relatively few deaths from COVID-19 and local officials have been among the most vocal opponents of the two-month shutdown.
Calabria in the south allowed bars and restaurants with outside tables to open to the public on Thursday.
But areas of the north have also begun to open up.
Veneto region, which was among the first to be hit by the virus but has suffered far fewer deaths than neighbouring Lombardy, lifted a range of restrictions including on takeaways, pizzerias and some shops on Monday.
"We cannot allow the efforts made to be in vain because of rashness at this delicate stage. Moving from the policy of 'let's close everything' to 'let's reopen everything', would risk irreversibly compromising these efforts," Conte said.
While some businesses have been allowed to reopen, the lockdown will not begin to be lifted nationwide until May 4 and even then it will happen gradually over a series of weeks.
Conte said officials would carry out some 150,000 tests in May to see how many people were developing antibodies to fight the virus. An app to trace contacts between potentially infected people would be voluntary, he said.
Evidence of a rise in infections could lead to restrictive measures being reintroduced locally.
The virus reproduction number (R0) in Italy was currently between 0.5 and 0.7 -- meaning 10 virus sufferers infect between five and seven other people. Should it rise again to 1.0, intensive care units would once again be overwhelmed, he said.
Conte's speech to the lower house was delayed after opposition members complained that the prime minister was not wearing a mask.
The League party, whose members took off their own obligatory masks, forcing the speaker to temporarily suspend the session, spent Wednesday night occupying both chambers of parliament.
The far-right party's head Matteo Salvini has accused Conte of extending the lockdown because it was the easy option and stripping Italians of their fundamental freedoms.
He has said his party was deliberating whether to join grassroots protests called for Saturday.
Conte said the accusations were "profoundly unjust" and the saving of lives was a "primary good" that trumped other rights.
His lockdown may be unpopular but it was not an electoral programme designed to please anyone, he said.