Family First, headed by national director Bob McCoskrie, will fight a decision to strip the group of its charitable status. (File photo)

Advocacy group Family First has lost its appeal to have its charitable status reinstated.

The controversial group, whose objectives include opposing abortion, euthanasia and same-sex marriage, was stripped of its charitable status by the Charities Registration Board last year.

The board said Family First did not exist solely for charitable purposes, one of the criteria for being classed as a charity and therefore not being required to pay income tax.

FRANCES FERGUSON/STUFF Family First promotes a traditional family set-up and strongly opposes abortion, euthanasia and same-sex marriage. (File photo)

In a High Court decision, Justice Simon France backed the board's decision, saying Family First's agenda was not charitable or in the public interest.

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"The board considers that Family Trust has a purpose to promote its own particular views about marriage and the traditional family that cannot be determined to be for the public benefit in a way previously accepted as charitable," the judge said.

It is the second time the group has been stripped of its charitable status.

In an earlier ruling, the Charities Board based its decision on a premise that any group which promoted a political agenda could not be charitable.

But based on a Supreme Court precedent, that assumption was later refuted and Family First successfully appealed.

This time, while acknowledging a charitable organisation could still carry a political purpose, the judge ruled Family First had not acted objectively in its cause.

"Family First has not satisfied me the board erred in its decision. Its core purpose of promoting the traditional family unit cannot be shown to be in the public benefit in the charitable sense under the [Charities] Act.

"Further, it has other purposes, some of which have previously been held to be non-charitable, and the rest of which present a weaker public benefit argument than the core purpose."

The judge said promotional material circulated by the group was "merely a method of presenting its advocacy to the public".

Rather than advancing education on topics discussed, Family First had simply expressed a "one-sided perspective intended to persuade the public to a particular point of view".

Of all its publications, only one of them - based on research from the New Zealand Institute of Economic Research - was capable of being objective, but even that failed, the judge said.

"As with other reports, the media release accompanying the report does not present the results objectively, and instead uses them in a manner that advances Family First's views."

Family First says it will appeal the decision.