The NUJ has stepped up its campaign against proposals to place advertising on the BBC's international website, BBC.com.
A decision from the BBC Trust on the matter is expected in the coming months, after the Trust postponed making a decision and agreed it needed more information from BBC management.
According to the NUJ, more than 200 reporters, editors and correspondents have signed a petition opposing the plans to carry ads on international-facing BBC web pages.
The union has today leafleted BBC staff as part of its ongoing campaign. It argues that the plan "would permanently damage the BBC's distinctive reputation abroad, and in the UK, as an independent public service broadcaster".
The NUJ general secretary, Jeremy Dear, said: "The BBC should not launch itself down this slippery slope. The public, in the UK and overseas, do not want to see the creeping commercialisation of a world-renowed public service broadcaster.
"They respect the BBC for its editorial integrity, its public service values and its ad-free space, all of which are under threat from this crass commercial adventure."