Updated 6.38pm: The father of Down Syndrome baby Leo Forrest has pleaded not guilty to a charge of assault.

Samuel Forrest has appeared in the Waitakere District Court today facing a charge of assaulting the trustee he asked to help look after a fund of hundreds of thousands of dollars raised in a public campaign to bring his son back to New Zealand.

It's alleged the 37-year-old assaulted Tina Mclachlan earlier this month at the rented home he shares with his Armenian wife in Massey and seven month old son.

The male-assaults-female charge carries a maximum penalty of two years in jail.

The judge lifted name suppression when Forrest pleaded not guilty.

He's due to appear in court again in September.

According to NZME, McLachlan became co-trustee of the fund at Forrest's request, but earlier this month went public with concerns about how the money was being spent.