FILE PHOTO - The GlaxoSmithKline building is pictured in Hounslow, west London June 18, 2013. REUTERS/Luke MacGregor/File Photo

LONDON (Reuters) - GlaxoSmithKline's GSK.L research and development head Patrick Vallance is set to leave the drugmaker to become the British government's new chief scientific adviser, a person familiar with the matter said on Friday.

His planned departure comes three months after GSK’s new Chief Executive Emma Walmsley announced a major shake-up in the pharmaceuticals division and said the group needed to do better in drug development by adopting a sharper commercial focus.

Vallance, who joined GSK in 2006 and has been president of R&D since January 2012, has not yet officially resigned. When he does so, GSK will be obliged to issue a statement, since he is also a board member.

GSK declined to comment on Vallance’s exit, which was first reported in the Financial Times. The British government was not immediately available for comment.

In his new job, Vallance - a one-time professor of medicine at University College London - will replace Mark Walport as the senior science adviser to the prime minister and other officials. The exact timing of that handover is unclear.

The move is a further sign of change under GSK's new boss Walmsley, who earlier this year poached Luke Miels from AstraZeneca AZN.L as her new head of pharmaceuticals. Miels will be a key lieutenant in driving productivity improvements.

GSK has lagged behind rivals in recent years in producing multibillion-dollar blockbuster drugs. It has also suffered a number of high-profile clinical trial failures on Vallance’s watch, undermining faith in its R&D skills.

In a bid to turn things around, Walmsley said in July she would narrow the focus of the group’s drug research by ditching more than 30 drug projects. GSK will in future allocate 80 percent of its R&D budget to respiratory and HIV/infectious diseases, along with two other potential areas of oncology and immuno-inflammation.

Walmsley’s plans for overhauling Britain’s biggest drugmaker have yet to fully convince investors, many of whom worry that the dividend could be risk if she twins a revamp of pharma with a big acquisition in consumer healthcare.