With BP on the slide again, the oil and gas sector is today's worst performer.Shares in BP are down more than 5%, resuming their drop following a couple of days' respite.In its latest update, the oil giant said it has spent another $350,000 (£234,000) on the Gulf of Mexico oil disaster since Monday, taking the total cost to date up to $2.35bn (£1.57bn) and the number of people dealing with the response effort to some 37,000.Not all stocks in the sector are suffering. Peru-focused oil producer Maple Energy is higher even though it lost $12.45m before tax in 2009 versus $5.17m the year before, as lower oil prices sent revenue down to $64.70 from $95.29m in 2008.Defensively orientated stocks, such as the cigarette suppliers British American Tobacco and Imperial Tobacco, are in demand.Top performing sectors so far todayAlternative Energy 5,372.63 +2.09%Mobile Telecommunications 3,358.81 +1.48%Industrial Transportation 2,256.05 +1.46%Tobacco 25,639.73 +1.27%Banks 4,708.44 +1.11%Bottom performing sectors so far todayOil & Gas Producers 6,312.25 -2.42%Forestry & Paper 4,293.46 -1.82%Mining 20,454.89 -1.67%Industrial Metals & Mining 5,326.90 -1.58%General Retailers 1,584.94 -1.54%