Being in government obliged his party, albeit briefly, to take part in the business of political compromise, itself a moderating experience.

ECONOMIST: A conundrum for Austria��and for Europe

As a lifetime senator, Mr Monti cannot run for office but can take part in an election campaign and can return to the post of prime minister if asked by a party or coalition.

BBC: Vatican paper backs Mario Monti's Italy leadership bid

Prof Bogdanor told Today presenter James Naughtie that retired members of the armed service "have every right to take part in the political debate, " but added that former personnel "must not appear to align themselves with a political party, " particularly in the build up to a general election.

BBC: Guthrie comments 'beyond acceptable'