Former Christian Heritage Party leader Graham Capill has admitted to indecently assaulting a young girl under the age of 12.

Capill has admitted a representative charge of indecently assaulting the girl between 2001 and 2002. He had no objection to his identity being revealed.

The victim was eight years old at the time of the offending, which occurred three or four times. It involved indecent fondling while she was in bed in her pyjamas.

Capill fronted the morally conservative Christian Heritage party for 13 years and has most recently been working as a police prosecutor, presenting cases in the Christchurch District Court.

The police say Capill is suspended from his police duties pending his sentencing for indecent assault. They say it is inappropriate for their Prosecutions Department to comment on employment issues personal to Capill.  But they say given his guilty plea, that will now be considered from an employment perspective.

Last month, as Capill was leaving the Christchurch District Court, he was punched in the face twice and knocked to the ground by Daniel McNally. Capill's lawyer, Jonathon Eaton, jumped in and pulled McNally off Capill, who lay on the ground sobbing.

McNally was charged with one count of assault and Capill was taken to hospital to have his jaw x-rayed.

The leader of the Christian Heritage party, Ewan McQueen, says he is deeply shocked by Capill's admission of indecently assaulting a child. McQueen says Capill's shameful actions were destructive to the victim and also brought reproach on the party and the wider Christian community.

McQueen says he's still coming to terms with the news. However he says Capill has played no role in the Christian Heritage Party since 2003 and had recently resigned his membership.

Capill has been remanded on bail until next month for sentencing. The maximum penalty is 10 years in jail.