Retail stocks were trading lower on Friday with heavyweights Marks & Spencer and Tesco providing a drag on the sector.M&S was off shopping lists today after Goldman Sachs retained its 'sell' recommendation for the British department store chain, saying that the business could feel the heat from the recent increase in competition in the grocery market.In a research report dated April 3rd, the bank added the stock to its 'Conviction Sell List' and slashed its target price for the shares from 420p to 340p. The stock was down 1.3% at 465.7p this afternoon."With circa 50% of its revenue [for the year ended March 2014] coming from UK grocery sales, we do not believe M&S will be immune to escalating competition in UK food retail," Goldman said.The comments came ahead of M&S's fourth-quarter trading update on April 10th, which Goldman expects will show flat like-for-like (LFL) sales in Food and another quarter of LFL declines in GM.Supermarket giant Tesco was trading 1.1% lower on speculation that its Finance Chief Laurie McIlwee could quit amid falling profits and a recent decline in market share. According to the Financial Times, the McIlwee, who has worked for Tesco for 15 years, could leave the company in the coming days, citing people familiar with the situation. His possible departure would leave Chief Executive Philip Clarke as the only executive director left on Tesco's board. The FT's sources said that McIlwee had "clashed" with Clark over some areas of the company's strategy.B&Q owner Kingfisher was also among the worst performers on the FTSE 350 on Friday, along with SuperGroup and Ocado.Home furnishings retailer Dunelm was also in the red, pulling back following a strong rise on Thursday after impressing the market with its third-quarter update. Food wholesaler Booker was extending losses after underwhelming with fourth-quarter figures yesterday. Top performing sectors so far todayIndustrial Metals & Mining 1,076.81 +3.42%Forestry & Paper 11,665.38 +2.75%Mining 17,164.16 +1.83%Automobiles & Parts 9,511.25 +1.78%Life Insurance 7,073.99 +1.68%Bottom performing sectors so far todayTechnology Hardware & Equipment 1,220.44 -1.17%Food & Drug Retailers 3,827.66 -0.97%Mobile Telecommunications 4,887.15 -0.86%General Retailers 3,035.23 -0.66%Household Goods & Home Construction 11,482.35 -0.27%BC