GlaxoSmithKline is investigating fresh allegations that staff in China were involved in paying backhanders to doctors to sell Botox in China, according to the Wall Street Journal.

The newspaper says it has reviewed internal GSK documents and emails which show that sales staff were apparently instructed by local managers to use their personal email addresses to discuss marketing strategies related to Botox (onabotulinumtoxin A), Allergan's drug which GSK sells in China for therapeutic indications. The WSJ claims that in the personal emails, employees discuss rewarding doctors for prescribing Botox with cash payments, credits that could be used to meet medical-education requirements and other rewards.

The WSJ had previously reported that an anonymous whistle-blower presented GSK in January with allegations that between 2004 and 2010 its staff provided doctors with speaking fees, cash payments, dinners and all-expenses-paid trips in return for prescribing its products. The allegations led to an internal probe, which GSK has previously said turned up no evidence of corruption or bribery.

A GSK spokesman told the WSJ that the Botox-related allegations may have come from the same source who has made previous claims of alleged corruption and bribery. Noting that no evidence was found to support the previous allegations, "nevertheless, we are investigating these new claims".

The spokesman added that "our inquiries to date have found no evidence of bribery or corruption in relation to our sales and marketing of therapeutic Botox in China". Last week, in an unrelated story, it emerged that senior staff at GSK in China had been under police investigation for "economic crimes", while the country's National Development and Reform Commission has begun an inquiry into pricing practices at 60 drugmakers.