The BBC investigation, which will be broadcast tonight, claims that the company may have violated the UK Bribery Act and the US Foreign Corrupt Practices Act, which make it illegal for companies to bribe government employees abroad.
GSK issued a response this morning saying it had taken disciplinary action and was co-operating with the Polish authorities.
It said: "Following receipt of allegations regarding the conduct of the programme in the Lodz region, GSK has investigated the matter using resources from both inside and outside the company. The investigation found evidence of inappropriate communication in contravention of GSK policy by a single employee. The employee concerned was reprimanded and disciplined as a result."
It added: "We agree there is a need to modernise interactions between the pharmaceutical industry and healthcare professionals to ensure patients’ interests are always put first and to eliminate even a perception of a conflict of interest.
"This is why we have made, and will continue to make, fundamental changes to our business such as opening up access to our clinical trial data, changing how we pay our sales representatives and stopping payments to healthcare professionals for speaking engagements and for attendance at medical conferences."
Following a corruption scandal in China last December, GSK announced changes to its incentive schemes including an end to direct payments to doctors for promotional talks and a stop to setting individual targets for its sales representatives.