Nectar members would usually receive two points for every £1 spent in BP Connect stores. However, this will not apply to M&S products sold via the Simply Food trial.
Eight BP Connect stores will carry the Simply Food concessions, with BP aiming to extend the partnership if the trial is a success.
The tie-up, announced by the two companies in May, will mark the first time M&S products have been sold next to other brands.
It is believed that Nectar's contractual obligations to Sainsbury's stop BP from awarding points for M&S products.
The Simply Food trial is part of BP's plans to refine its forecourt offer and take market share from the convenience sector.
BP Retail marketing director Chris Sedgewick said the Simply Food format would co-exist with its Wild Bean Cafes. He added that the company still plans to extend the cafe format across further sites. Wild Bean Cafes are currently in more than 170 of BP's 1250 forecourt sites.
BP Retail will launch its first TV ad campaign this month. In the past it has relied on radio and press advertising.
The ad, created by Ogilvy & Mather, will work along similar lines to BP's 'Gourmet to go' radio campaign.