The Attorney General's Office said it received complaints about the jail terms or community punishments received by nearly 400 criminals in 2011.
Law officers looked in detail at 117 cases and after they were considered by the Court of Appeal, 97 were deemed too soft and all but three were increased.
It is the largest number of sentences to have been ruled unduly lenient since 2006, when 113 were highlighted. In 2010, just 65 were deemed too light.
Among the sentences judged too soft last year was one handed down by Cherie Booth, Tony Blair's wife. She spared a drug dealer jail after he was caught with a kilogram of cocaine worth £145,600, in what was described as a "startling result". He was given three and a half years behind bars after the case was considered again.
"In the vast majority of cases judges impose sentences which are appropriate to meet the justice of the case, but the scheme provides an important safeguard in those few cases in which the sentence falls significantly outside the proper range."
One of the most senior judges in England and Wales said only a "tiny fraction" of the cases heard in crown courts last year led to sentences being increased.
The President of the Queen's Bench Division and Deputy Head of Criminal Justice, Sir John Thomas, said: "These statistics show that, as in previous years, the number of sentences found to be unduly lenient is very low.
"As ever it is important to note that sentencing can often be a complicated process which requires judges to weigh a wide range of factors."
