A group of five consumer advocates are asking federal regulators to reject H&R Block Inc.’s attempt to open a savings bank, saying the company could use it to take advantage of low-income customers.

The Kansas City, Mo.-based tax preparation giant applied in May to open the savings banks. It said it wanted to provide a cheap banking alternative for tax clients and other customers who don’t typically use mainstream banks.

But the advocates worry that H&R Block could use the bank to expand the sale of tax refund loans, which has led to several class action lawsuits protesting high fees for low-income customers, as well as push subprime mortgages in poor neighborhoods.

A bank would represent a big revenue pop for H&R Block, which now must park more than $1 billion of its customers’ money in a network of partner banks. Operating its own bank would save the company from having to pay those banks fees.