** Credit Suisse downgrades Britain's Marks & Spencer to "underperform" from "neutral"
** In Feb, M&S and Ocado announced an online food joint venture that would allow M&S to sell its full range of food online for the first time, by replacing Waitrose on Ocado platform in September 2020
** CS says M&S's response to fragmentation and loss of market share for Clothing & Home is to try to double market share of Food and make it a full shop, hence the Ocado JV
** However, says this is coming at a time of increasing competition for its core offer and sees long-term pressure on LFL sales and margins
** Says JV is a direct threat to Waitrose, which will be competing hard to convert customers from Ocado to its own online offer
** CS lowers EPS forecasts by 16% and 27% for next two years with risks to downside, also reduce its target price to 250p from 315p
(Reporting By Geetha Panchaksharam)