The upmarket fashion retailer plans to relocate production overseas, with a loss of more than 300 jobs.
Workers planned to picket the 800-guest party, due to be held at the Natural History Museum in London on February 10, to get maximum publicity for their already high-profile campaign.
Burberry chairman John Peace said he was very disappointed by 'attempts to disrupt this premier event' for the British film industry. He said that the company was an active supporter of the British arts and 'wholly committed to Britain', with almost half of the group's global workforce based in Britain.
GMB union spokesman Mervyn Burnett said: 'We had no plans to disrupt any Bafta event and suggestions by Burberry that we did is completely wide of the mark. GMB's intention was to peacefully point out that Burberry is planning to move 310 jobs from south Wales to China for the sole purpose of cutting polo-shirt production costs from£11 to£4, raising profits by using non-unionised, super-exploited Chinese textile workers.
'We have requested guarantees from Burberry that they will not use child labour or enforced prison labour in China to manufacture its merchandise. These guarantees have not been forthcoming.'
Rhondda AM Leighton Andrews said: 'Burberry is cracking under the pressure that's being exerted. It's clearly very concerned about the impact on its image and reputation.'
The GMB plans to hold simultaneous international campaigns on Valentine's Day outside stores in Las Vegas, Paris, New York and San Francisco, called Stop Burberry Breaking Our Hearts.