The next time you step up to the register, beware the cashier promising freebies in exchange for signing up for a store credit card.

Interest rates on cards issued by the nation’s largest retailers are averaging 23.24 percent, according to a new survey by credit card comparison site Creditcards.com, based in Austin, Texas. It’s the highest rate since the website started tracking the rates in 2008 (when they averaged 18.28 percent).

Overall, the average for all types of credit cards is 15.22 percent.

“With their outrageously high (rates), most consumers would be wise to steer clear of these cards unless they’re 100 percent certain they can pay their balance off every single month,” said Matt Schulz, senior industry analyst at Creditcards.com.

The survey reviewed 68 credit cards offered by 44 retailers. Nearly half of those store-branded cards carried an annual percentage rate of at least 25 percent.

Among the stores with the highest rates were Big Lots at 29.99 percent, Zales at 29.24 percent and Staples at 28.24 percent.

Those high rates look even worse considering that interest rates in general have been hovering at record lows since the Federal Reserve cut the federal funds rate to near zero at the end of 2008, where it remained until seeing a tiny quarter-point boost in December last year.

The chief reason that retailer cards tend to charge higher rates than general-purpose cards is to compensate for the risk involved with extending instant approval at the register. The main lure among store cards is an immediate 10 percent or 15 percent discount at the check-out as a bonus for signing up.

While the discount might pay off on a major purchase such as a refrigerator, most shoppers can get better rewards with a general purpose card, Schulz said.

“Bonuses you get with a store card can’t compare … so you’re better off shopping around for another card,” he said.

Sign-up bonuses have gotten sweeter in the last couple of years as card issuers compete for the best customers, he said.

For example, the Chase Freedom Unlimited card offers a $150 cash back bonus for spending $500 in the first three months.

“Percentage-wise, a store credit card can’t come close to matching that offer,” Schulz said. The Chase card also carries an introductory interest rate of 0 percent for the first 15 months, which rises to between 14.24 percent and 23.24 percent, depending on a customer’s creditworthiness.

“It’s important that people don’t get pressured into making a bad choice” at the register, Schulz said.

“If you are interested in an offer, take a brochure and read it at home. If you’re still interested, apply the next time you go to the store.”