The financial fallout of relationship failure hits mums the hardest with 73 per cent worse off after a break-up than their ex-partner, according to new research from AUT.

Dads fared a little better with 38 per cent being worse off financially than before the split.

The financial consequences of close to 16,000 parents who separated during 2009 were analysed by AUT business senior lecturer Dr Michael Fletcher.

In a world first, Fletcher followed the economic fortunes of pairs of ex-partners up to three years after separation using anonymised data. Researchers aren't usually able to link the partner's data. All the couples had children including step children, grandchildren and other arrangements.

Fletcher's analysis found in 46 per cent of the separations the man gained financially compared to their ex-spouse, after taking into account the change in their family size. In around a quarter of cases both were worse off.

Relationship failure can have the effect of pushing many former couples and their children into poverty.

The research found the collapse of a relationship led to large increases in poverty. Compared to a matched comparison group of similar people who did not separate, poverty rose 16.4 percentage points for the women and 8.8 percentage points for men. This impact lasted for the three years after separation.

He told Mike Hosking that benefit numbers go up.

"The income that the separated women get from welfare goes up dramatically."

Fletcher chose the area of research as there is a lot of focus on sole-parents in poverty but no information on what happens when people split up. Over the last six years Fletcher used the Working For Families database to analyse what occurred when a couple separates.

Fletcher hoped the research would be used to reassess how welfare system and child support payments operated.

- with content from NZ Herald

LISTEN TO MICHAEL FLETCHER TALK WITH MIKE HOSKING ABOVE