LONDON — British police and the country’s leading child welfare group drew a horrific picture of more than 200 cases of sexual abuse of children as young as 8 by the television host Jimmy Savile in a report released Friday, and prosecutors admitted for the first time that they could have brought Savile to trial before his death in 2011 but failed to do so.

The depiction of what Peter Spindler, a police commander, called a ‘‘vast, predatory and opportunistic’’ record of misconduct offered the latest gruesome indictment in a scandal that has plunged the BBC, Savile’s longtime employer, into crisis; drawn in a mounting tally of suspects and victims; and raised questions about the protection of children in supposedly safe institutions.