Italy's controversial budget plans, which have spooked financial markets and attracted criticism from the EU, are backed by a clear majority of voters, a poll showed on Sunday.

Some 59 per cent of Italians back draft budget plans for 2019, which foresee a substantial deficit hike, an Ipsos survey published by the Corriere della Sera newspaper indicated.

In a comment, Ipsos Italia President Nando Pagnoncelli wrote that he also found that 55 per cent of Italians believe that a higher government debt is needed to stimulate the economy.

Rome's ruling populist parties are planning to raise the deficit to 2.4 per cent of gross domestic product (GDP), from 0.8 per cent set by a previous government.

This has raised concerns in Brussels and among investors because Italy's debt levels are already among the highest in the world, standing at more than 130 per cent of GDP.

On Monday, the Italian government is due to send written explanations to the European Commission, which has warned Rome against an "unprecedented" deviation from eurozone budget discipline rules.

On Saturday, Deputy Premier and Five Star Movement leader Luigi Di Maio ruled out toning down deficit plans, even after a downgrade of Italy's credit worthiness by Moody's ratings agency.

But Cabinet Secretary Giancarlo Giorgetti, of the League party, told Sunday's Il Messaggero newspaper that the 2.4-per-cent deficit target was a "maximum ceiling," hinting that it could be lowered.

"We cannot always have our foot on the gas. If we see a bend ahead of us, we should brake and change down a gear, and accelerate afterwards," Giorgetti said.