Gavin Neath, president of the Food and Drink Federation (FDF) and chairman of Unilever UK, said the industry was near a point where it could not make fresh cuts in salt levels.
He warned that further moves could spark a consumer backlash and lead to foreign imports flooding the market with salted products.
However, the campaigning group Consensus Action on Salt and Health said the industry's arguments were based on commercial imperatives not health concerns.
The FDF, whose members include Nestle and Coca Cola, unveiled a study of the impact of its Food and Health Manifesto, launched in September 2004, which set out a series of commitments on reducing levels of salt, sugar and fat, and introducing smaller portions.
It revealed that 36% of products contain less salt than in 2004 and 56% are now offered in more than one size, although these include 'sharing' or family packs.
Health campaigners accuse the industry of being sluggish over portion sizes, saying groups such as Cadbury continue to develop bigger bars and packs in the guise of 'sharing sizes'.
The FDF plans a consumer awareness campaign next year, in partnership with the Department of Health, to promote healthy eating.