Maia said he would oppose any proposals along the lines of a so-called "digital" tax from the government. He also dismissed Guedes' arguments that the new tax would compensate for payroll tax exemptions.

"I will work against it, as I have already said. I will even work so that it will be defeated at the Constitutional and Legal Affairs Committee, so Brazil does not enter into this nightmare of creating taxes at every crisis," Maia said during an online event hosted by Banco Santander.

"Paulo (Guedes) says it is not (a new) CPMF. If the minister says that he should present the proposal, send an official constitutional amendment to debate the matter," Maia said.

He was referring to an unpopular financial transactions tax that was abolished in Brazil in 2007.

Guedes has suggested that some form of the tax is needed to fund payroll tax cuts or exemptions.

Guedes and his team are putting together a wide-ranging reform of Brazil's complex tax system, which they hope will simplify tax payment and collection, make it easier and more efficient to do business, spur investment and boost growth.

(Reporting by Eduardo Simões; Writing by Jamie McGeever; Editing by Tom Brown)