It shows that as well as achieving the highest CTR, smartphone clicks are cheaper than the corresponding desktop and tablet clicks.

Furthermore, tablet CPCs saw the most significant growth during 2012, averaging a 36% increase in the UK compared to 24% for smartphones and 14% for desktop.

It will be interesting to see how Google’s recent shift to Enhanced Campaigns will impact mobile CPCs during 2013.

The new method of managing PPC means that advertisers will be able to target people based on the time of day, their location and the device they are using.

The idea is to simplify AdWords by allowing users to manage their campaigns in one place, but it also means that advertisers no longer have the ability to run mobile-only campaigns.

But despite the encouraging performance in terms of CTR and CPC, it’s the same old story for smartphones when it comes to conversions.

Marin’s report shows that smartphones achieved a conversion rate of just 1.6% in the UK during 2012, compared to 2.6% on tablet and 4.1% on desktop.

This supports data from Kenshoo, which found that tablets delivered 18.3% of UK paid search conversions in 2012 and 21.3% of revenue, while smartphones achieved just 3.6% of overall retail conversions from PPC and 3.4% of revenue.

It also reported that the conversion rate from smartphone visits is just 1.59% compared to 5.85% on tablet and 6.53% on desktop.

Overall, Marin’s report shows that the proportion of UK paid clicks from smartphones and tablets almost doubled during 2012, from 14.8% in January to 24.4% in December.

In comparison, the proportion of mobile clicks on Google in the Eurozone jumped from 5.9% to 14.5%.

However mobile search ad budgets are still slightly behind clicks, with the share of spend on mobile increasing from 9.94% to 19.32% during 2012.

Meanwhile, Eurozone advertisers upped their investment in mobile search from 4.8% to 11.8% of paid-search budgets.

Marin’s data comes from brands and advertisers that annually spend more than $4bn on paid search.