The prime minister's comments come after PdL Secretary Angelino Alfano, deputy prime minister, broke away from Berlusconi's party to create the New Centre-right political group.
"I think what happened will help stability in Italy. It will create a clearer situation in which people will take their own responsibility," Letta said at the Financial Times Future of Italy Summit 2013 in Rome on Monday.
On October 2nd, the Letta government won a no-confidence vote with Alfano's backing after Berlusconi demanded his five PdL ministers resign from the fragile coalition government.
"What happened is the application of the decision in parliament on October 2nd, I think the situation is more stable," the prime minister added.
Since Berlusconi was defeated there has been widespread speculation about a possible breakaway group or party formed by Alfano.
A visibly weary Berlusconi on Saturday expressed his "sadness" at the decision by Alfano, who stayed away from the PdL meeting with around 50 defectors.
Speaking on Monday, Letta also dismissed the suggestion of divisions within his own Democratic Party (PD), following criticism from Matteo Renzi, Florence Mayor and PD politician tipped for the leadership.
"I think we are on the same path with Renzi and the PD, because next year will be a year in which we have to apply reforms which are important from the political point of view."
"I am sure that Renzi and the others [within the PD] will be very much on side; they know that institutional changes will be effective," Letta said.