* Berlusconi risks rare grilling on hostile talk show
* Trying to close big gap with centre-left
* TV watchdog says Monti getting too much air time (Recasts, adds details from La7 broadcast)
By Steve Scherer and Gavin Jones
ROME, Jan 10 (Reuters) - Seeking a fifth term as Italian prime minister, Silvio Berlusconi took his election campaign into risky and unfamiliar territory on Thursday when he appeared on a television programme run by some of his fiercest critics.
Desperate to close a wide gap with the centre-left less than seven weeks before the vote, Berlusconi surprised many observers when he said he would attend a talk show hosted by a journalist who has made a career out of criticising him.
The 76-year-old media tycoon is far more accustomed to appearing on his own television channels, where the questioning is anything but challenging and he is seldom interrupted.
"I love playing away games," Berlusconi was quoted saying in a tweet on his campaign's Twitter page before the broadcast, and another tweet said, "In a few minutes, president Berlusconi enters the lion's den".
Italy's most proven political campaigner and savvy media mind appears to have made the right choice ahead of the Feb. 24-25 parliamentary election.
Berlusconi successfully made some of his key campaign points and deflected thorny questions about "bunga bunga" sex parties, which he denies staging, and his claims that he was the victim of an international plot to oust him from power.
Berlusconi resigned in 2011 as borrowing costs soared and he faced a sex scandal involving an underage prostitute, and Mario Monti took his place to save Italy from a disastrous Greek-style debt crisis that threatened the existence of the euro.
Although the journalist, Michele Santoro, had his show on the state broadcaster cancelled after Berlusconi accused him in 2002 of making "criminal use" of his programme, all seemed forgiven as the two engaged in a mostly friendly tit-for-tat throughout Thursday's broadcast.
Only during the final minutes, when Berlusconi denounced Marco Travaglio, an editorialist who also appears on the programme, for being a "professional slanderer", were there sparks - when Santoro got angry.
Berlusconi's latest appearance on Santoro's "Public Service" talk show on La7, a private channel he does not own, was the latest in a dizzying series of radio and television interviews he has done to try to close the gap ahead of the vote.
Most recent polls put Berlusconi's centre-right around 26 percent, trailing Pier Luigi Bersani's centre-left which has a commanding lead at around 38 percent, with outgoing Monti's centrists around 15 percent of the vote.
Monti has also been a daily presence on Italy's talk shows and radio programs, and Italy's telecommunications watchdog said on Thursday he was getting preferential treatment from state broadcaster RAI and other channels as he campaigns.
Monti shed his image as a non-partisan technocrat when he announced last month he would seek a second term in office and has been campaigning furiously at the head of a coalition of centrist parties.
The telecoms authority AGCOM said that after two weeks of the campaign there had been unacceptably uneven coverage of the parties contesting the election, and it called for an "immediate adjustment".
In particular, it said Monti was being given too much air time on the news programmes of two of RAI's three channels and was also getting the lion's share of coverage on private broadcasters Sky Italia and La7.
AGCOM chastised Berlusconi for his appearances on his own broadcaster, Mediaset, that favoured his People of Freedom party (PDL).
AGCOM said that if its "strong call" for more balanced coverage was not heeded it would take more concrete action, which in the first instance would involve fines for the offending broadcasters. (Reporting by Gavin Jones; Editing by Mark Heinrich)