New buyers were the biggest driver behind a 22 percent increase in online holiday retail sales last year, a research firm said Monday.

In its "Holiday 2004 Postmortem" report, JupiterResearch, a division of Jupitermedia Corp., said online retail spending in November and December rose to $22.1 billion.

The increase in sales last year over 2003 was driven largely by an influx of new online buyers, the research firm said. About 17.7 million consumers made an online holiday purchase for the first time in 2004.

In addition, three quarters of the online shoppers bought from a site they had never purchased from before, JupiterResearch said.

"The holidays present a great opportunity for retailers to acquire new customers for the long term," Patti Freeman Evans, retail analyst at JupiterResearch, said in a statement.

Online retail sales this year is expected to surpass $79 billion, up from $66 billion last year, according to JupiterResearch.