Authorities in China first accused GSK last July of funnelling up to 3 billion yuan ($480 million) in bribes to encourage doctors to use its medicines in a case that the company described in 2013 as "shameful".
Since then allegations have surfaced in other countries and GSK is now investigating claims that bribes were also paid to doctors in Poland, Iraq, Jordan and Lebanon.
The allegations that bribes were paid in Poland could be particularly damaging, according to some lawyers, since the country belongs to the European Union and GSK would be expected to uphold the same standards there as in any other EU state.
Despite the barrage of bribery reports, GSK has insisted it does not have a "systemic issue with unethical behaviour" and says it has a clear system for dealing with violations, which resulted in 48 dismissals and 113 written warnings last year.
In a bid to try and put the problems behind it, GSK is rolling out a new sales model designed to eliminate sharp marketing practices.
The firm aims to become the first in the industry to stop paying outside doctors to promote its products, end payments for medics to attend conferences and delink incentives for sales representatives from individual sales targets.