A growing number of shoppers in the US went into cyberspace for Christmas this year, but returning unwanted gifts may end up giving a hangover to consumers and e-tailers alike.

Online sales for the holiday season are expected to reach about $6 billion this year, according to various market surveys. But returns may put a crimp on the race to e-commerce.

Some Internet sites have no policy on returns or charge fees for returning unwanted merchandise. Others that have brick-and-mortar stores may allow customers to return the items. "Very few of these e-tailers will get it right this year," said Mr Malachy Kavanaugh of the International Council of Shopping Centres.

"It's not just a lot of trouble (to return Internet gifts), it can be expensive for the gift recipient. I'm sure that's not what the giver intended."

Extraprise Advisors, a Boston consulting firm, said 13 of 50 sites surveyed required a telephone call for returns, and 10 said fees may apply, including some for "restocking". But some of the sites do not clearly state their policy on returns.

"Last year there was some `ignorance is bliss'," said Mr Allen Bonde, the consulting firm's research director.

"People were just happy they could shop online. This year it's the morning after and people are saying, `Wow, this should be a lot better'. We expect a lot of hiccups and bumps and bruises."

"It's a huge problem," said Ms Britt Beemer of America's Research Group, a consulting firm in Charleston, South Carolina. "People aren't going to put up with the cost and aggravation."

Some experts recommend negotiating with the retailer to reduce or eliminate return fees. But some sellers may have policies that are complex. Wal-Mart, for example, will not take back lingerie. Others will only take items back in their original packaging.

"I don't shop online because I can't figure it all out," Ms Beemer said. "That's not my fault. I'm the customer and that means I'm right. That's their problem."