Marks & Spencer has told the groceries inquiry it would be happy to be covered by a strengthened Supermarkets Code of Practice - but insisted any tightening of the code should not require all retailer-supplier agreements to be put in writing.

Responding to the commission's provisional findings, M&S - which is not currently covered by the code - said it would also like to participate in the process of drawing up any new version.

"If the commission concludes that grocery retailers are engaging in practices that are having an adverse effect on suppliers, which are not currently covered by the code, then it would be appropriate to enhance the Code of Practice to address these," M&S said.

However, it warned that greater recording in writing of dealings with suppliers "could become a hindrance to both retailers' and suppliers' ability to compete when competitive conditions in the market for a particular product change".

M&S also told the commission a distinction should be drawn between retrospective changes to contractual terms, which should be prohibited, and other practices which should be subject to the current reasonableness test.

If the code was extended, then symbol groups should also be covered, it contended. "Symbol groups should also be included within it to ensure uniform standards for the treatment of suppliers exist throughout the industry," it said.

The retailer also agreed with proposed remedies designed to prohibit the use of restrictive covenants and exclusivity agreements on land and property.