GlaxoSmithKline's growth profile could get a lift from next year as a number of elements, including legal charges, drop out of the drugmaker's new key measure of core earnings.

The shift to reporting core earnings per share (EPS) brings Britain's top drugmaker into line with international peers like Novartis and AstraZeneca , which already use this as the main metric for their financial reporting.

GSK, which announced in July it was changing the way it reports results to give shareholders clearer visibility of our anticipated progress in 2012 and beyond, presented further details on the move in a briefing for analysts on Thursday.

Legal costs have proved a persistent drag on profits across the drugs industry in recent years, following a slew of patient liability claims and an increasingly aggressive stance by U.S. authorities over cases involving mis-selling of medicines.

Four other factors will also be excluded from GSK's new definition of core EPS -- other operating income and profits on disposals; amortisation and write-offs of intangible assets; major restructuring costs; and accounting adjustments related to material acquisitions.

Up until now, GSK has focused on earnings before major restructuring.

Setting out the impact of the change, which will take effect from the first quarter of 2012, GSK said that core EPS in 2010 would have been 125.5 pence, rather than 53.9p reported under the old before-restructuring system.

The big difference reflects the fact that massive legal costs were taken in 2010 related to the settlement of claims over its Avandia diabetes drug and sales practices for a range of other products.

For the first nine months of 2011, core EPS would have been 84.4p -- or slightly less than the 85.8p reported before restructuring -- due to an exceptional gain on the disposal of GSK's remaining stake in Quest Diagnostics in the first quarter.

Mark Clark, an industry analyst at Deutsche Bank, said he expected earnings in future years to get an uplift of around 5 percent from the change in reporting practice.

Analysts at Jefferies had said in a note on November 21 their provisional analysis indicated a 9 percent earnings uplift from the move in 2012.

GSK has been through a difficult few years, due to a wave of patent expiries and a collapse in sales of Avandia after it was linked to heart attack risks. But the group is now expecting better times as the effect of these big hits start to wane.

(Reporting by Ben Hirschler; Editing by Paul Sandle)