By Roberto Landucci
ROME (Reuters) - The Italian government said on Tuesday it would put its bitterly contested electoral reform to a confidence vote in parliament, forcing rebels in Prime Minister Matteo Renzi's center-left Democratic Party (PD) to back him or face new elections.
The announcement by Institutional Reform Minister Maria Elena Boschi prompted shouts of anger from opposition politicians, who accuse Renzi of seeking a power grab with the bill, which is one of the government's chief reform priorities.
In combination with a separate shake up of the Senate, the new law, which has been under discussion for more than a year, is designed to leave a clear winner after a general election by awarding a generous "majority premium" to the leading party.
Critics say the bonus is excessive and undemocratic. They are also unhappy about provisions that would let party chiefs handpick some candidates, saying they would concentrate too much power with the leadership.
But Renzi said that after years of revolving door governments and failed promises by successive administrations, the law had to be changed and he challenged the opposition and dissidents in his own party to take him on.
"The lower house has the right to get rid of me if it wants, that's what a confidence vote is for. As long as I'm here, I will try to change Italy," he tweeted after the announcement.
Renzi has a majority of around 70 seats in the lower house or Chamber of Deputies which would be at risk if all the PD rebels voted against the bill.
However, with the PD rebels heavily divided themselves, it remains unclear how many would actually be ready to collapse the government and Renzi has so far faced down attempts by dissidents to derail the plans.
A do-or-die confidence motion sweeps away all amendments to legislation before parliament. If the electoral reform bill is approved unchanged in the Chamber of Deputies it will become law, but it will only take effect in July 2016.
(Writing by James Mackenzie; Editing by Crispian Balmer)