HALF a billion dollars spent buying back hundreds of thousands of guns after the Port Arthur massacre had no effect on the homicide rate, says a study published in an influential British journal.

The report by two Australian academics, published in the British Journal of Criminology, said statistics gathered in the decade since Port Arthur showed gun deaths had been declining well before 1996 and the buyback of more than 600,000 mainly semi-automatic rifles and pump-action shotguns had made no difference in the rate of decline.

The only area where the package of Commonwealth and State laws, known as the National Firearms Agreement (NFA) may have had some impact was on the rate of suicide, but the study said the evidence was not clear and any reductions attributable to the new gun rules were slight.