Glaxo, which makes everything from Aquafresh toothpaste to Horlicks, has faced bribery allegations in China in recent months, and similar accusations of corruption in Poland and Iraq.
The SFO investigation is understood to be focused on whether the business failed to prevent bribery across several jurisdictions. The agency confirmed the investigation but did not give further details.
The SFO’s escalation of the issue is likely to undercut Glaxo boss Sir Andrew Witty’s attempt to defuse the controversy in recent weeks.
Edison analyst Dr Mick Cooper said: “This looks more serious than what has happened in China, this is the first time the SFO has investigated a major pharma company in the UK.”