Italy's grass-roots Five-Star Movement on Monday introduced a bill to cut members of the lower house of parliament's salaries by half.
"This law could be approved within days enabling savings of up to 87 million euros a year," the movement's leader Beppe Grillo wrote on his blog announcing the bill.
He has called on activists to rally outside Italy's parliament on Tuesday to support the initiative.
Grillo claims the saving would be more than that estimated in reforms to Italy's political machinery being put to voters in a referendum on 4 December. Centre-left premier Matteo Renzi has staked his political future on the constitutional reforms.
The reforms include replacing Italy's 315-member upper house of parliament Senate with a leaner, largely consultative body containing local mayors and regional councillors, the government claims to streamline the law-making process and reduce its costs.
The reforms would cut the number of senators to 100 from 315 currently but would leave the size of the lower house of parliament unchanged at 630 lawmakers.
Italian MPs have a basic gross salary of 10,000 euros a month but under the Five-Star movement's rules, its MPs pledge to accept half of their base gross salary of over 10,000 euros a month.
Renzi on Sunday said MPs' pay should be linked to their attendance records and that one of the Five-Star movement's leading figures, Luigi Di Maio, only had a 37 percent attendance record.
De Maio, who is deputy lower house of parliament speaker, says his attendance figures belie Renzi's claim.
