Smartphones — Apple and Google’s in particular — were the driving force in mobile phone sales last quarter, according to a report issued by Gartner early Wednesday.

Worldwide smartphone sales to end users reached 54.3 million units in the quarter, up 48.7% year-over-year. The overall mobile phone market, by contrast, grew only 17%, to 314.7 million units.

“In the first quarter of 2010, smartphone sales to end users saw their strongest year-on-year increase since 2006,” said Gartner’s Carolina Milanesi, who pointed out that Apple’s (AAPL) iPhone OS and Google’s (GOOG) Android were the only two smartphone operating systems among the top five to increase market share year-over-year.

Apple’s smartphone OS market share grew to 15.4% from 10.5%, according to Gartner. But Android is gaining fast, having jumped to 9.6% from 1.6%, leapfrogging Microsoft (MSFT) Windows Mobile in the process. Nokia (NOK) Symbian is still No. 1, but it’s losing ground in market share, as is No. 2 Research in Motion (RIMM). (See Table 2 below the fold.)

In the worldwide market for mobile phones, not just smartphones, Apple climbed to No. 7 on the strength of its best quarter to date. End user sales of the iPhone worldwide grew 112% year-over-year, according to Gartner. (See Table 1 below)

“Growth came partly from new communication service providers in established markets, such as the UK, and stronger sales in new markets such as China and South Korea,” said Milanesi. “The second quarter of 2010 will be a very important one for Apple. We expect that Apple will present its new iPhone in June during its Worldwide Developer Conference, which will be the first to feature the latest release of the iPhone OS that includes welcome improvements for developers and users, such as multitasking.”

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