"Tests indicate that a large proportion of customers receive significant doses, used in combination with many common medications, and, in most cases, alternative treatment methods are being replaced by medication," Ombudsman Juris Jansons said in a report focused on patients at 30 public mental health institutions across the county of two million.
"Customers simultaneously receive multiple medications and high doses. Many clients receive these drugs in combination even though they are not relevant to their disorder in treatment guidelines," he claimed, adding that "many clients receive treatment against their will, which is illegal."
"We now expect action from the parliament; the remedy should be rapid," he told reporters.
Jansons' report also slams everything from the poor quality food provided, to patients being forced to use buckets as toilets and others kept for long periods in solitary confinement.
According to Welfare Ministry statistics, around 13,000 people live in social care homes in Latvia, of whom nearly 7,000 are classed as having mental health or developmental problems.
The allegations prompted the ministry to announce it intends to launch a probe into practices at its care homes.