Heseltine is fronting the charge against the OFT on behalf of the magazine and newspaper industries, press wholesalers and newsagents.
The letter, which has been copied to senior ministers, including Tony Blair and the secretary of state for culture, media and sport, Tessa Jowell, criticises the OFT's draft opinion. It also complains about the office's handling of the process.
The OFT has been investigating the legality of the current magazine distribution system since late last year. Its draft opinion recommended an end to territorial monopolies, giving retailers the freedom to choose wholesalers.
Heseltine's letter explains that far from enhancing competition, the recommendation will reduce it between retailers, magazines and newspapers, between magazines themselves and between wholesalers. It also complains about the OFT's lack of understanding of the industry and its unwillingness to engage in discussion with it.
A spokeswoman for the office said: "The OFT was asked by the industry to consider the legality of its distribution system. It was asked to give an opinion and it's unfortunate that the opinion is not the one the industry wants. The industry is reacting disagreeably to the opinion it asked for."
A final opinion is expected in the next few weeks.