NEW YORK – Citigroup Inc., 18 percent owned by the federal government, is testing a website to let millionaires’ children manage their allowances while alerting parents and bankers when scions blow through cash too quickly.

Heirs to Citigroup’s wealthiest clients can log in to parent-funded accounts for discretionary spending, investments and “one-click giving” to charities. The site was developed by Tile Financial, founded by former New York Stock Exchange finance chief and Bear Stearns analyst Amy Butte.

Banks are trying to nurture relationships with clients’ children to ensure fortunes aren’t transferred to other financial advisers as wealth shifts to the next generation, Butte said in an interview. New York-based Citigroup made a minority equity investment in Tile last month, said Chris Kay, head of the bank’s Growth Ventures and Innovation unit.

“Intergenerational wealth transfer is a very big issue for the industry,” Butte said, adding that $1 trillion will be inherited in the United States through 2025. “Even if we’re half-wrong, it’s still hundreds of billions of dollars.”

The Tile portal, called Spend Grow Give, is available to clients of Citigroup’s private bank, which caters to people with more than $25 million, including a third of the world’s billionaires. Young heirs can get spending accounts linked to debit cards, and they can craft investment portfolios in consultation with a parent’s private banker.

Tile plans to introduce electronic alerts sent to the parents if their child spends an allowance too early in the month, said Butte, 42.

Butte got the idea after seeing her husband, a money manager, stumble while discussing finances with her four stepchildren, ages 17 to 23.

“Young adults have no place to go to learn about money and learn about finance, particularly in a tone and a medium that they can relate to,” she said.