The Scottish Legal Aid Board has warned that significant further savings are required to keep the system sustainable.
The cost to the taxpayer fell in 2012-13, while running costs and staff numbers are also down, according to the board's annual report.
Chief executive Lindsay Montgomery said: "Although some grants of legal aid can attract negative public or media attention, legal aid provides people with important help at vulnerable times in their lives. It is also there to pursue cases in pursuit of the public interest, such as clarifying new areas of law.
"But the fact remains that even after the savings that have already been delivered and the savings that we expect to deliver in future years, the level of legal aid expenditure expected in the next two years is above the Scottish Government's spending plans. Substantial additional reform of the wider justice system is also planned which will impact further on legal aid expenditure."
Savings must be found while protecting access to justice without the "drastic" limitations to the scope of legal aid in other countries, he said.
Money from the Government to meet running costs has been reduced by 26% in real terms since 2007 and is planned to drop further.
Staff numbers have been cut by 12% over the past three years.
At the same time, the board expects workloads to increase, including an expected 20,000 applications for children's legal aid as a result of changes to the hearings system.
The annual accounts show expenditure on the legal aid fund was £150.2 million, which is about £7.4 million lower than the previous year.
Civil legal assistance spending fell by 9.1% to £49 million, while applications increased by nearly 4%.
Spending on criminal legal assistance fell 3.7% to £94.8 million, driven by falling levels of summary criminal business in courts.
Board chairman Iain Robertson said: "The legal aid system in Scotland is highly regarded the world over. Its scope and eligibility when compared to many other countries, and its demand led nature, are all reasons for that.
"The savings packages developed by the board and the Scottish Government, and negotiated with the legal profession, saved over £18 million last year. But the pressure on public expenditure continues.
"In tandem with our justice sector partners we will work to protect this important public service in the future."