* Grillo wants change to "pigsty" electoral law
* Calls for cancellation of vote expenses, two-term limit
* President urges parties not to rule out deals
By Naomi O'Leary
ROME, March 2 (Reuters) - The 5-Star Movement that emerged as Italy's largest party after a deadlocked election might support a government if it changed electoral law, cut politicians' expenses and set a two-term limit for parliamentarians, its leader has told a magazine.
Parties have been wrangling over how to form a government as neither 5-Star, the centre-left group led by Democratic Party (PD) leader Pier Luigi Bersani nor the centre-right group led by People of Freedom (PDL) party head Silvio Berlusconi won full control of parliament in this week's vote.
"If Bersani's PD and Berlusconi's PDL suggest an immediate change in the electoral law, cancellation of election expenses reimbursement, and a maximum of two terms for any deputies - we would of course support such a government immediately," comic Beppe Grillo told German magazine Focus in an interview published on Saturday.
"But they won't do that. They are just bluffing to win time," Grillo added.
"If we get into parliament we would bring the old system down, not because we would enjoy doing so but because the system is rotten."
In a blog posted on his website, Grillo said his party would not give a vote of confidence to any government but would only consider backing individual laws.
A majority of parliamentarians must back confidence votes - which are called regularly in Italy's parliament as a way of speeding through laws - in order for a government to keep its mandate.
In a statement on Saturday, Italian President Giorgio Napolitano urged parties to be realistic and not to categorically rule out making agreements with each other.
"We all have a duty to safeguard the public interest and the international image of the country," he said.
Napolitano, whose term ends in May and whose successor must be appointed by parliament, has ruled out a return to the polls.
On Friday Bersani said he would present a programme based around a limited number of points, many of them in line with Grillo's platform, and seek the support of parliament.
"You can call it what you want, a minority government, a government of limited purpose, I don't care," Bersani told newspaper La Repubblica.
Changing the electoral law known as "the pigsty", which makes it difficult for parties to form stable governments, has been called for by both the centre right and centre left.
Currently, the party that wins the most votes nationally is awarded at least 55 percent of seats in the lower house. However, seats in the Senate are decided in separate regional votes, which means the party with a majority in the lower house may not control the upper house, as in the current case.
Both houses have equal lawmaking powers so control of both is required to govern. The last government, led by Mario Monti, tried to change the electoral law, but politicians did not manage to agree on a bill before the government fell in December.
In the interview with Focus, Grillo described Italy as "overwhelmed, not by the euro, but by debt" and said he expected new elections within six months.
He insisted his party would win a majority in a second vote. "This is a dress rehearsal," he said of this week's election.
Grillo did not himself run for a seat in parliament as he holds a criminal conviction, which excludes him under his own movement's rules.