An expert says Victim Support is right to be tentative when giving out the money donated to families affected by the Christchurch mosque attacks.

The organisation has come under fire for handing out only $3 million of the $14 million raised for the families of the Christchurch terror attacks.

Charity lawyer, Sue Barker, told Mike Hosking charities are subject to rules and regulations, but this is an unprecedented case.

"There are a lot of victims and they may not have all come forward yet and the key pressure on Victim Support is that they must do it in a fair and consistent way," she said.

"They can't just do a lolly scramble, if they give all the money away and then victims come forward later there would be another story complaining that they didn't have a fair and consistent process."

She said it's also hard to know how many victims there actually are.

"There are 51 dead, 50 injured, I don't know how many others might have been in the mosque as well, then there are potentially immediate families members affected and the number of victims could be 800 or 1000."

"If you divide $10 million by 1000, actually you only have about $10,000 per vicitm and they have actually already paid to some victims $15,000 or more...$10 million is not a lot of money when you think about how many victims there are," Barker said.

Barker said defining who is and isn't a victim is also an issue that needs to be dealt with.

"It's a complex process and I really do think they are doing there absolute best."