Sony has posted a 47% fall in quarterly profit, hurt by its struggling mobile phone joint venture with Ericsson.

Net profit at Sony fell to $326 million in the period April to June, causing Sony to lower its forecast for the financial year by 17%, citing the slump at Sony Ericsson and fierce competition as rivals try to undercut its Cyber-shot digital cameras and Vaio laptops.

Sony said operating income from its electronics division tumbled as much as 57% during the quarter, on severe price competition in the digital and video camera segments, although sales and profitability improved on its Bravia range of liquid crystal display televisions.

Sony slashed its net income forecast for the full-year ending March 31, 2009, to 240 billion yen, 17% lower than the company’s May estimate of 290 billion yen. The Japanese electronics giant also expects full-year sales of 9.2 trillion yen, 2% higher than it projected in May.