The appointment is likely to herald a watershed in the history of the voluntary sector, coming as it does in the same week as the publication of the draft Charities Bill.
In her Third Sector column, Peacock has made no secret of her dislike for the monikers "charity" and "voluntary sector", and it is likely she will use her new position to attempt to carve out a new 'brand' for the sector. This could involve changing the name of the Charity Commission and even of the Charities Bill, should it eventually become an act.
It is also understood that she would favour a widening of the commission's role to encompass the whole not-for-profit and social enterprise sector, not just registered charities.
Her appointment was made after a review by the Prime Minister's Strategy Unit that saw the expansion of the commission's responsibility as regulator and the creation of new roles of part-time chair and full-time chief executive. The chief executive is in the process of being appointed.
Peacock, who was voted most admired charity chief executive in Third Sector's Most Admired Charities survey last year, will give up her roles as interim chair of Futurebuilders and civil service commissioner.
She was previously chief executive of Guide Dogs for the Blind until she became a charity commissioner in July 2003.
Charities Minister Fiona Mactaggart said: "Geraldine brings a huge amount of experience, and will stand up effectively for the voluntary sector in Whitehall."
Peacock will succeed chief charity commissioner John Stoker when his term of office ends in July, and she will become chair when the Charities Bill is implemented.
The NCVO says it will launch a ministerial lobbying campaign if the draft Charities Bill, due to be published tomorrow, fails to reform the role of the commission so that it is prevented from acting as an adviser to charities while policing their activities.
"We want the commission only to regulate," said NCVO spokesman James Georgalakis. Part of the NCVO's remit is to advise charities. Earlier this month, the NCVO formed the Coalition for a Charities Act, a group of 22 of the biggest charities campaigning for the bill to be passed in Parliament in 2005.
But the NCVO's position appears to be at odds with some of the charities it represents. Turning Point, for example, contends that regulating and advising functions can be complementary.