The Commission, which replaced the Legal Ombudsman in 2008, has so far awarded more than £250,000 in compensation or rebated fees for inadequate professional services, according to its annual report.
It received 1123 complaints in 2012/13 and says poor communication by lawyers is at the root of a "staggering" 57% of all cases - only 4% are about fees.
It also says complaints overall are down 8% since 2008, but they are increasing in the most complained-of areas, led by residential conveyancing, which accounts for 19% of the total, followed by litigation (16%) and family law (15%).
The Commission added: "Almost a fifth of practitioners did not refer dissatisfied clients to the SLCC and we are continually finding examples where practitioners have not signposted clients to us.
"We are working with consumer bodies such as Which?, Citizens Advice Scotland and the Office Of Fair Trading to ensure information about the SLCC is both up to date and more widely accessible."
Complaints about professional misconduct are still referred to the Law Society Of Scotland and Faculty Of Advocates.
The number of complaints submitted to the Commission this year was down from 1264 the previous year. Almost half of the complaints dealt with were upheld last year, against one in three upheld by the English legal ombudsman.
The Commission says that is down to better complaint screening, and the successful use of mediation. It says the handling cost per complaint is down 37%, and about 50% of grievances are now resolved between practitioner and client.
Chief executive Matthew Vickers said: "We encourage parties to mediate, and we run a free in-house mediation service. Typically, if you can get both sides involved in mediation the success rate is about 75%."
He said people were sometimes put off because they thought they "had to be in the same room" in mediation with the lawyer they were complaining about, which was not the case.
Mr Vickers said the Commission was in discussions with the Law Society Of Scotland, consumer groups and academics over reforming the system whereby any appeal against a Commission decision had to go through expensive litigation in the Court Of Session.
He said the commission was about to review the operation of the Law Society's Guarantee Fund, intended to protect the public against fraud by solicitors.
The SLCC was also concerned about the difficulty of securing redress for clients when a law firm went bust and a judicial factor or trustees were involved.
"The complainer is just a creditor the same as anyone else," he said. "There is no point in having a complaints system where, at the end of it, people can't get redress. You are putting people through a wringer not to get the redress they deserve."
Commission chairman Bill Brackenridge said: "I would encourage the profession to continue to work closely with the SLCC to promote best practice, further reduce the number of complaints and continue to improve the reputation of the legal sector".