Plans by Italy's populist parties to leave the euro and cancel Italy's debt if they form a government have been condemned as unrealistic by analysts.
To help reduce Italy's public debt, which at more than 130 percent of national output is the highest in the eurozone after Greece's, the joint document calls for the ECB to forgive €250 billion of Italian benchmark BTP bonds bought under the bank's so-called "quantitative easing" program.
Di Maio shrugged off such warnings as the protests of "Eurocrats that nobody elected", while on Wednesday Salvini, attacked European Union commissioner Dimitris Avramopolous' request that Italy's new government not change its policy on migration.
But the coalition quickly retreated, claiming the text, dated May 14, was "an old version that has been considerably modified".
The League and 5-Star have failed to agree on forming a coalition between themselves after an inconclusive election on March 4, but they have enough votes together in parliament to block any other government from taking office. Both parties have made clear they intend to fight the EU's Stability Pact.
Five Star Movement leader Luigi Di Maio told reporters on Wednesday afternoon that "Salvini and I are ready to remain outside" a potential government team, if this was necessary to make the deal work.
Italian election pictures: Who will win the election in Italy?Berlusconi, 81, has warned the 5-Stars are risky for Italy and its democracy.
5-Star deputy Alfonso Bonafede also said the policy document was completed.
With Italy now writing the rulebook to its future relationship with the EU, Brussels has been left powerless to push back.
Mr Piccoli described the Commission as "very weak and on its way out".