Ms Sweet, a legal journalist and solicitor, took up her new job this week, providing the first national focus for pro bono work undertaken by solicitors. That will include commissioning research across the whole profession, developing best practice models and liaising with existing free legal advice services.
Ms Sweet, 32, former news editor of the Solicitors' Journal, says: "There is already some concern at the high-street level that this is a big City guilt-appeasing act. But that is not what it is all about and I hope we can counter that effectively once solicitors see what we are doing.
"Despite public perceptions of the legal profession, pro bono work is carried out extensively but it is mostly done on an ad hoc basis - weekly sessions at a local Citizens' Advice Bureau or sitting on the board or trustees for a charity.
"What we need to do is establish a clear picture of the sort and amount of pro bono work that is being carried out and then promote best practice models across the profession."
One immediate problem will be deflecting public expectations that the group can provide a referral service for individual cases - every mention in the media prompts dozens of pleas for help.
"I have already had a letter from a windmill restoration charity asking for free legal advice," Ms Sweet says. "However, we just do not have the information or resources to run a referral unit at this stage."
Pro bono - short for pro bono publico ("for the public good") is a buzz phrase, used by those annoyed by raucous headlines pillorying "fat cat lawyers".
In some American states law firms are obliged to give a percentage of their time to pro bono work but there is no such obligation here. However, lawyers have been providing free legal services for many years - the Bar's Free Representation Unit has for 25 years provided law students, trainees and young lawyers to represent people in industrial, social security and immigration tribunals, for which legal aid is not available.
"Making pro bono obligatory here just would not work," Ms Sweet believes. "If you look at what is happening in the high street, with many firms facing an uphill struggle to survive, that kind of regulation would just explode in the profession's face.
"What we have to do is show firms the benefits of providing pro bono work in terms of training, broadening experience and improving links with the local community."
However, that will mean overcoming the old concern that pro bono work could be used as an excuse for cuts in legal aid.
"Pro bono work is not intended to replace legal aid," Ms Sweet emphasises. "But, realistically, legal aid is not going to increase whatever the complexion of the government so there will always be a huge gap of unmet legal needs which the profession should be helping to bridge.
"Talking to the Government about the future of legal services in the light of the Middleton report, for example, will be high on our agenda."
Part of the challenge of raising the group's profile will be winning the profession's financial backing through membership fees. Several large law firms, including Allen & Overy, Clifford Chance, Dibb Lupton Broomhead, Herbert Smith and Linklaters & Paines, have covered the group's first year budget of pounds 100,000 and promised a similar amount to underwrite the second year. But the group, which is a registered charity, is committed to being self-financing within that period.
Alongside its research work, the group is likely to lobby for changes to make pro bono work more attractive.
Mark Stephens, of Stephens Innocent, is a member of the SPBG's executive committee and is keen to see it take on a "proselytising role". He believes more lawyers would do work free if they could claim their costs from the losing side when they won. Pro bono clients should also have the same protection from having to pay their opponents' costs if they lost that litigants on legal aid enjoyed.
For the Bar Pro Bono Unit, which has been running a referral service for the past year, one priority is to encourage more solicitors to make use of its panel of 720 barristers, which includes 120 QCs.
Vanessa Simms, the unit's administrator, says less than 20 per cent of the 450 cases that have come into the unit have been referred by solicitors.
"The number is disappointing as there is a big need for the service we offer but perhaps the word has not got around yet among solicitors. The vast majority of cases come directly from members of the public but quite often they are also in need of a solicitor so our ability to help them is quite limited"
The Solicitor's Pro Bono Group is at 15 St Swithin's Lane, London EC4; tel 0171 929 6601/2/3. The Bar Pro Bono Unit is on 0171 831 9711 and the Bar's Free Representation Unit on 0171 831 0692.