ROME (Reuters) - Italian Prime Minister Mario Monti cannot be a candidate in next year's parliamentary election as he is a Senator for life, but he could be involved in forming a government afterwards, President Giorgio Napolitano said on Thursday.

The head of state's comments add a further twist to a complicated tale as speculation had been growing that Monti, a technocrat and former European Commissioner, could be persuaded to join a centrist bloc before the vote.

Napolitano said on a visit to Paris that Monti's position as Senator for life, a title bestowed last year just before he became prime minister, meant that he could not run as a candidate for parliament.

Monti "is a Senator for life, he can't stand for parliament because he's already a parliamentarian. He hasn't been a private citizen for a little time, even if sometimes it's forgotten", Napolitano told reporters in remarks broadcast on Italian TV.

Monti's non-elected government, drafted in to bring stability at the height of last year's financial crisis, has been widely credited with restoring Italy's international credibility after the scandal-plagued era of Silvio Berlusconi.

Many members of Italy's business establishment would like him to serve a second term after the election, and Monti himself has said repeatedly he would be available if no workable government could be formed.

Napolitano said Monti had an office in the Senate in Rome "where he will be able to receive anyone, after the election, who wants to ask an opinion, a contribution or a commitment".

Monti has always said he would not stand as a candidate in the election itself, but speculation has grown that he could throw his weight behind a centrist grouping, such as the movement set up by Ferrari chairman Luca Cordero di Montezemolo.

However the remarks from the head of state appear to rule out definitively any direct involvement in the campaign.

In a statement issued later, Napolitano's office said the president was not offering any opinion on what government should be formed after the election.

"The President of the Republic is not endorsing any option for a government after the election," the statement said.

Pier Luigi Bersani, head of the centre-left Democratic Party which is leading in opinion polls and which supports the government in parliament, urged Monti this week not to run to avoid affecting his role as a figure above the party fray.

The Democratic Party has nonetheless suggested Monti could continue to play a central role in political life, possibly as president when Napolitano steps down in May.

(Writing By James Mackenzie; editing by David Stamp)