Morrisons has said it will re-run adverts on sustainable fish, despite Sainsbury's and four members of the public lodging complaints with the ASA.

In the first of the two TV ads, actor Robert Lindsay was shown pushing a trolley through a stream saying he wanted fresh fish from a sustainable source. A second ad was broadcast in the same break, featuring Lindsay speaking to a fishmonger about cod. The complainants said this implied cod was sustainable and the ASA said it had reached an informal agreement with Morrisons not to show the ads until it had substantiated the claims on sustainability.

Morrisons said it was confident it could back up its claims and was planning to use the ads again.

"We have informally resolved the case and agreed not to re-run the advert until there is an agreement on substantiation which, on the basis of our evidence, we are confident will be achieved soon," a Morrisons spokeswoman said. "Retailers have a responsibility with regard to products' integrity. Hence we are completely transparent and have led the way with our labelling across our fish range."

Sainsbury's customer director Gwyn Burr said retailers needed to ensure any claims about sustainability could be proven. "We all need to be very certain of the claims we make to customers," she said.

An ASA spokesman said that if Morrisons decided to broadcast the ads again, it could prompt more complaints, which the ASA would have to investigate.