Retailers need to embrace mobile technology and develop vertical-specific strategies to help increase sales in a more competitive environment, according to eBay.

Speaking at the ChannelAdvisor Catalyst 2011 conference in London, Clare Gilmartin, VP of market places, Europe, at eBay, said that mobile was increasingly breaking down the barriers between the offline and online retail worlds.

"Our belief is that those worlds will become totally blurred over the next few years. What's the thing that's driving the change? It's mobile.

"It's important that retailers have a mobile presence," said Gilmartin.

Last year, eBay predicted that mobile would generate $1.5 billion (£0.9 billion) in sales globally, and that in the UK, an item would be bought every 15 seconds. Gilmartin said that actual results show that the company's estimate was conservative.

"It [mobile] generated $2 billion in 2010 [with $4 billion expected for 2011] and one item is bought in the UK every two seconds," she said.

eBay's mobile revenue was driven by smartphone and iPad apps, such as a fashion application that allows users to virtually try on sunglasses.

In December last year, the company boosted its mobile development capabilities with the acquisition of Critical Path Software, which builds applications for mobile phones and desktops.

"Innovation in mobile will help drive us to innovate faster online as well," said Gilmartin.

Another side to eBay's growth strategy was to target vertical markets.

The company sells across 13,000 categories, to a very broad set of buyers. It decided to target buyers more specifically, in an effort to improve conversion rates. It decided to target the fashion vertical first, which is the company's strongest vertical market in Europe.

"Increasingly we are tailoring [shoppers'] experiences. For example, in fashion, images are really important," Gilmartin explained.

She said that the tailoring of shopping experience on eBay has helped drive a "step change" in the fashion category. The site has four million unique visitors a month to the fashion category of, and most of the items - 61 percent globally - are sold at a fixed price, rather than at an auction price.

"We want to apply this approach to other verticals, such as electronics, home and garden and auto parts," she added.

Gilmartin said that mobile and verticalisation "will not go away". Another area where she sees growth opportunities is in cross-border trading.

"Twenty percent of eBay business is across borders (as of Q4 2010). Internationalisation brings huge sales opportunities - do you have systems in place to take payment, ship and provide customer service across markets?" she said.