The row, which is expected to provoke more protests against restrictions in the coming days, erupted as Italy registered 34,505 new coronavirus cases on Thursday and 445 fatalities – the highest daily death toll since April 23.

“It’s a slap in the face for Lombardy,” argued the president of Italy’s industrial heartland, Attilio Fontana, a member of the far-right opposition League party who has accused Prime Minister Giuseppe Conte of using out-of-date figures to divide the country into different zones.

Lombardy was designated “high-risk” on Wednesday, along with fellow northern regions Piedmont and Valle d’Aosta, and Calabria, which forms the southern toe of the Italian peninsula.

Southern regions Puglia and Sicily were designated orange, or medium-risk, and will also face further restrictions.

The rest of Italy was yellow, including the hard-hit region of Campania.

There was widespread confusion and anger after Conte announced the classification on Wednesday night, with many wondering how regions with some of the lowest case numbers – Calabria and Valle d’Aosta – had ended up as red zones, while regions with many times more, including Campania, Lazio and Veneto were classed as only medium-risk.

The regional classification, however, isn’t based on case numbers alone, but on a complex system of 21 criteria established by Italy’s Higher Health Institute (ISS), including hospital capacity.

And with little official explanation given to the public as to how the system works, some critics insist the decision was a political one.

The opposition League party accused the centre-left government of locking down regions run by the opposition while going easy on those run by the left – insisting Campania, run by the Democratic Party (PD), should not be a yellow zone.

Valle d’Aosta President Erik Laveva told the regional assembly: “Yesterday I reiterated that it is important to have clarity about why we are in a red zone, in part to give clarity to the citizens.”

“Numbers are nice because they don’t lend themselves to interpretation,” he added.

Calabria’s acting governor, Nino Spirlì, said the region would challenge the government’s decision to make it a red zone.

Anger and concern about the system was not confined to red zones.

Those in orange zones also questioned the fairness of the decisions, while some in yellow zones voiced concern that their hard-hit local areas required tougher restrictions.

Campania alone is currently reporting around 4000 new cases per day, many of them concentrated in the city of Naples.

However, the region was classified a lower-risk yellow zone.

The mayor of Naples, Luigi de Magistris, complained that the region should be a red zone, insisting local hospitals were overwhelmed and at risk of collapse.

He said the government’s maths “does not add up”. 

Piedmont head Alberto Cirio, from the centre-right Forza Italia (FI) party, also questioned why the decision over which regions to lock down “was taken based on data which was at least 10 days old”.