Workers in the criminal and family courts across England and Wales said cuts and court closures have put significant pressure on the service which is leading to mistakes being made.
Staff in one region, Durham Tees Valley, told a survey by Napo, the union for probation and court staff, that constraints had led to offenders getting off lightly.
"Possibly because of shortcuts, unpaid work requirements have been imposed where alternative, more robust sentencing was needed," said the union's report.
"Staff ... report a number of cases where curfew orders have been imposed in cases of domestic violence which significantly increases the risk of harm to victims."
Officials even reported cases in which the courts had imposed offending behaviour programmes on offenders as punishments - such as drink and drug courses - even though the programmes had been closed down.
In Hampshire, staff reported that closure of local courts to save money meant defendants frequently failed to turn up for hearings because they did not want to pay for the journey.
Offenders knew it may lead to their arrest, allowing them to travel to court for free in a police van, said the report.
Probation officers also reported receiving less information from the Crown Prosecution Service when they were asked to prepare pre-sentence reports.
"Staff report in one particular case, information covering a death by dangerous driving case was reduced to three pages of summary evidence," said the findings.
"It did not go into the details of how the victim had died or provide any information about victim impact family statements."
In the family courts staff reported delays of 12 to 16 weeks before cases could begin because of an "unprecedented" workload.
Harry Fletcher, assistant general secretary of Napo, said: "It is of concern that staffare reporting that often inappropriate sentences are handed down.
"The government justifies the cuts and closures in the grounds that it needs to save money.
"However, increased delays and adjournments will lead to increased costs in the medium and long term."
A Ministry of Justice spokeswoman said: "We are already taking forward reforms which will benefit victims and ensure more offenders are quickly punished with a sentence that fits their crime.
"These include maximising the use of videolink technology, improving the way agencies work together, removing bureaucracy and providing value for money.
"Recent court statistics show that the timeliness of cases dealt with in the courts has remained consistent over time but we want to improve this further."