LONDON, Dec 14 (Reuters) - Reports that British retailer Marks & Spencer (MKS.L) wants to increase its 50% stake in the Ocado Retail online supermarket joint venture with Ocado Group (OCDO.L) are "pure speculation", Ocado Group"s finance chief said on Tuesday. "That newsflow is pure speculation," Stephen Daintith told reporters after Ocado Retail updated on trading. read more "The partnership is working well. I think all three parties are working well with each other and we"re delighted with the progress that we"ve made and we"re excited at the prospect of a strong year of growth ahead of us," he said. Daintith said the prospect of M&S raising its stake "will always be a live potential transaction." "But right now there are absolutely no plans in that respect and everything is working well with the group and the joint venture," he added.