"Unfounded accusations" refers to claims or statements that are made without any credible evidence or justification. It means that the accusations are baseless, lacking truth or support. Full definition
Other times it is openly aggressive, such as unfounded accusations of child abuse or neglect. (illinoisdivorcelawyerblog.com)
Many have to continue teaching the child who made the accusation after the investigation has cleared them, and pupils may face no punishment for making unfounded accusations. (politics.co.uk)
Part of that code of conduct should be to refrain from unfounded accusations against professional scientists. (deepclimate.org)