If a sentence given in a Crown Court appears to be very low, or unduly lenient, anyone can ask the Attorney General to examine the sentence, within 28 days of sentencing.
The Attorney or Solicitor General may then ask the Court of Appeal to look at the sentence. The court may decide to keep the sentence the same, increase it, or issue guidance for future cases.
This includes the number of sentences examined, the outcome and details of the cases. Unduly lenient sentence data from before 2011 can be found at the National Archives
You can find guidance about unduly lenient sentences on complain about a low Crown Court Sentence