Online retail giant Amazon revealed a sharp drop in full year profits despite soaring sales.

Sales soared 41% in 2011 to $48.08bn (£30.54bn), however profits plummeted 45% to $631m (£400.76m) as the retailer continued to invest in the business.

Sales in its last quarter were up 35% to $17.43bn (£11.07bn) and profits dropped 58% to $177m (£112.4m) .International sales, which include its UK site, were up 37% to $7.53bn (£4.78bn) over the period.

The retailer is continuing its investment this year and warned that despite the fact sales are expected to grow between 22% and 36% in the first quarter, it could make an operating loss of up to $200m (£127m), which represents a decline of up to 162%.  

Over the nine weeks to December 31 the retailer’s Kindle sales soared 177% globally with its new version, Kindle Fire, its bestselling item worldwide and as well as in the UK.

Amazon chief executive and founder Jeff Bezos: “We are grateful to the millions of customers who purchased the Kindle Fire and Kindle e-reader devices this holiday season, making Kindle our bestselling product across both the US and Europe,”

Twice as many Kindles were sold in the run up to Christmas, compared to the year prior in the UK. The e-reader was the UK site’s biggest seller of the year and sales of Kindle books  grew five times higher than the previous year in the three months following the new version of the e-reader’s release.

In the UK, Monday December 5 was its busiest trading day in the run up to Christmas. More than 3m items were sold over the day, 35 items per second.