The two populist parties bidding to form Italy's next government have confirmed their intention to deport as many as 500,000 migrants if they come to power.

Repatriation of migrants was among the key campaign promises of the anti-establishment Five Star Movement and the far-right League in Italy's March 4 elections and is part of a common programme released on Friday for approval by their members.

About 600,00 migrants have crossed to Italy from Africa in the past four years. Some have already been sent back while others have been resettled in other European states, but most remain in the country.

The joint programme calls for Italy and the EU to implement bilateral agreements with other countries in order to speed up the repatriation of migrants, saying “today there are around 500,000 irregular migrants in Italy”.

The programme also pledged to close all "illegal" Roma camps, set up a register of imams and immediately shut down "radical Islamic associations".

If approved by party members, Five Star leader Luigi Di Maio, 31, and League chief Matteo Salvini, 45, will present their platform for governance to President Sergio Mattarella on Monday, along with a mutually agreed candidate for prime minister who has not yet been announced.

The programme promises the end of austerity in the eurozone's third-largest economy and seeks deep change in relations with the European Union. However, it contains no mention of a unilateral exit from the eurozone, mooted in previous versions leaked to media.

"The government's actions will target a programme of public debt reduction not through revenue based on taxes and austerity, policies that have not achieved their goal, but rather through increased GDP by the revival of internal demand," the document read.

And while an exit from the single currency is no longer proposed, the document announced the parties' intention to review "with European partners the economic governance framework" of the EU, including the euro.

The parties want a monetary union that is "appropriate for the current geopolitical and economic imbalances and consistent with the objectives of the economic union", it said.

Five Star became Italy's largest party at the March elections, gaining nearly 33 per cent of the vote, while the League - which was part of a right-wing coalition that won 37 per cent, won 17 per cent.

President Mattarella had earlier proposed appointing a non-partisan premier if none of the parties were able to agree on a viable coalition, but Five Star and the League have threatened to use their blocking majority to oppose such a candidate and trigger fresh elections.