The Italian prelate who was Pope Benedict's righthand man in the Vatican during his scandal-dogged papacy has defended his much-criticised record, insisting he "gave everything" to the job despite the activities of "vipers" in the Roman curia.

Speaking a day after Pope Francis named a Vatican diplomat as his new secretary of state, Tarcisio Bertone appeared defiant as he was asked about his time in office.

"I see the record of the past seven years as positive. Of course, there were a lot of problems, especially in the last two years," he said, according to the Ansa news agency, hitting out at "a combination of crows and vipers".

"But this should not cloud what I consider to be a positive record," he added. The Italian word corvo (crow) is used pejoratively to describe informants or people who leak secrets.

The final years of Benedict's papacy were overshadowed by scandal, most prominently the so-called "Vatileaks" affair that depicted the Vatican's swollen bureaucracy as a hotbed of conspiracy and cronyism.

Bertone, who was appointed by Benedict in 2006 to occupy a role often described as the Vatican's prime minister, was blamed for much of the papacy's disfunction and poor decision-making. The German pontiff came under pressure from some senior clerics to fire Bertone, but refused.

"I always gave everything but certainly I had my shortcomings," said Bertone, 78, on Sunday. "But this does not mean that I did not try to serve the church."

He said it was not true that the secretary of state "decides and controls everything" within the Vatican.

Announced on Saturday, the move to replace Bertone – which had been widely expected – has been greeted as a vital step forward in Francis's agenda for reforming the Vatican.

However, observers said the appointment of Pietro Parolin, a career diplomat who will return from his posting as nuncio in Venezuela to start the job on 15 October, signalled less a desire for wholesale reform than the wish to revive the old-style Vatican system that flourished under John Paul II.

Bertone had no diplomatic background when he was appointed, while Parolin served as Vatican undersecretary for relations with states – effectively deputy foreign minister – from 2002 to 2009.

He has worked in Nigeria and Mexico, and is known as a pragmatist rather than an ideologue who stayed out of the tense exchanges between the late Venezuelan president Hugo Chávez and the Catholic church.

"A veteran Vatican diplomat, Parolin … has been on the front lines of shaping the Vatican's response to virtually every geopolitical challenge of the past two decades," wrote John L Allen, of National Catholic Reporter, on his blog.

"By naming a consummate insider, Francis appears to want to 'reboot' the Vatican's operating system back to a point when it was perceived to operate efficiently, rather than scrapping it entirely."

Parolin, a 58-year-old Italian archbishop, said in a statement he would give Francis "complete availability to work with him and under his guidance for the greater glory of God, the good of the holy church and the progress and peace of humanity, that humanity might find reasons to live and to hope".