“I was given the invitation and I attended," he said.
"The fact that the Prince of Wales invited me clearly shows what I have done for the community since then.”
Mr Singh Rana, who lives in Walsall in the West Midlands, added: "I don’t know what checks they do or how they do them.”
Steve McCabe, MP for Birmingham Selly Oak, who sits on the Home Affairs select committee, said he was "flabbergasted" by the "astonishing" security lapse.
“There should be a police investigation into how this was allowed to happen. Who the prince wants to entertain in private is his concern, but this was a public event. Questions need to be answered," he said.
Mr Singh Rana was convicted of five counts of indecent assault, 11 counts of assault causing actual bodily harm and one count of attempted assault in August 1986.
At his trial, the court heard he posed as a doctor to con his way into the women's homes before subjecting them to internal examinations and giving them injections.
Faced with opposition to his inclusion on the Inner Cities Religious Council from the Sikh Secretariat in 2002, Mr Singh Rana said: "I have never tried to hide my convictions, even though the evidence presented was contentious. Are they saying rehabilitation and forgiveness should not exist? What I should be judged on is the work I've done in the Sikh community since that date."
