Apparel makes up the bulk of a mother's discretionary spending on her kids, a new report has revealed, with the age of the child influencing how much is spent.

According to the 'Kids' Share of Wallet' report from market research company The NPD Group, apparel accounts for 23% of discretionary spend.

And contrary to popular belief, it is not the household income that's the main driver of spending, but the age of the child.

Mothers who only have kids older than five years of age spend around 35% more than those with younger kids, while mothers of girls also spend more on apparel.

"Monitoring how and where parents spend money on behalf of their kids is critical information for anyone involved in the youth market," said Anita Frazier, industry analyst, The NPD Group.

"There are a lot of product categories competing for a fixed amount of discretionary spending, and understanding the factors that drive purchases has profound implications for product development, marketing, promotions, and licensing for all youth-oriented products and services."

Six out of 10 mums (59%) report their kids have a strong influence on the purchases they make for them.

Surprisingly, the category least impacted by kids' influence is apparel. Brand name influences footwear decisions, but is not a major factor for the other categories.

One factor that is important to purchasing decisions across all categories is the style and look of a product. Even at young ages, kids want products with appealing styles and designs.

Almost half of every discretionary dollar (48%) goes into entertainment related categories such as toys, books and music, the report found, while 12% goes on food and beverages.