Ruling on six complaints by Lever Brothers, the makers of Persil Power, against press advertisements for powders manufactured by Procter and Gamble, their main rival, the authority upheld three and rejected three.
The advertisements were placed last summer at the height of the "soap wars" between the two companies over claims that Persil Power damaged clothes.
The authority, after taking independent advice from safety experts, ruled that Proctor and Gamble had demonstrated their products were safer than those, such as Persil Power, with a manganese-based "accelerator".
However, it supported the complaints that Proctor and Gamble had made unsubstantiated claims that Ariel and Non-Biological Fairy were safer and more effective than all others on the market.
A statement from Lever Brothers, which has seen its share of the market fall since the introduction of Persil Power, said the company was delighted that the ASA had upheld three of its complaints.
"From the outset P&G have maintained that their attack on Persil Power and our unique accelerator ingredient was based on their evidence of a so-called manganese carry-over effect," Andrew Seth, managing director, said.
"The ASA adjudication shows this claim was unsubstantiated and we are pleased that the complaint regarding this most crucial issue has been upheld".
Proctor and Gamble maintained that the main Lever Brothers objection, namely that it had misled consumers over the extent to which products containing the accelerator were unsafe, had been rejected.
Earlier this month, the Consumers' Association claimed the "miracle" manganese catalyst ingredient of Persil Power could damage coloured clothing.
Clothes washed in the original Persil Power had only 40 per cent of the strength of those washed in Ariel Ultra, Persil's chief (non-manganese) rival, according to the association.
The tests were dismissed as unrepresentative by Lever Brothers, which is to launch an £18m advertising campaign for a new Persil product next week. The powder, New Generation, does not contain the manganese accelerator.Reuse content