Slaughter and May is advising global healthcare company GlaxoSmithKline (GSK) on a £650m move to increase its stake in its India and Nigeria subsidiaries.

The magic circle firm is has put forward a team under corporate partners David Johnson, Simon Nicholls and Richard Smith to advise GSK.

The deal, announced at the close of November, will see GSK increase its stake in its India subsidiary from 43.3% to 75% for a proposed sum of £591m.

Meanwhile, the healthcare company is planning to grow its ownership in its Nigerian arm from 46.4% to 80% for a price of £62m.

India's AZB & Partners is advising GSK on local law for the India transaction with a team led by M&A partner Ajay Bahl, while Nigerian firm Udo Udoma & Belo-Osagie is providing local law advice on the African asset, led by banking and finance head Daniel Agbor.

The transactions are subject to clearance and the offer will not formally be put forward until January 2013.

The news comes after Slaughters also advised GSK on the sale of a 10% stake in its joint venture company with Pfizer – ViiV Healthcare – to Japanese pharma group Shionogi last month.