Ex-BBC Norfolk broadcaster Michael Souter, 60, is standing trial at Norwich Crown Court, after pleading not guilty to 19 sex offences, including indecent assault, indecency with a child and serious sexual offences, against seven boys aged between 11 and 16.
The allegations date from between 1979 and 1999.
Souter, who is originally from Scotland, also denies a further nine counts of making and possessing indecent images of under-18s.
Souter, who was also involved in the Scouts and a youth mentoring scheme, said: "I have not committed these acts. These proceedings have had a devastating effect on me."
Asked why police found indecent images of boys on his computer, Souter said: "I have no doubt whatsoever somebody has been putting these images on my computer in an attempt to do me down."
The trial continues.