Mumbai, Aug. 19 -- Benchmark indices edged higher on Monday as the proposed goods and services tax (GST) revamp lifted hopes of boosting domestic consumption. Adding to the momentumwere India's sovereign ratings upgrade by S&P Global and a temporary relief for nations buying Russian oil. The Nifty 50 index ended Monday at 24,876.95 points, up 1% or 245.65 points, its highest gain since 23 May. The Sensex closed 0.83% higher at 81,273.75 points. Chirag Mehta, chief investment officer at Quantum Mutual Fund, said that while the GST rationalization announced on 15 August could drive up consumption, in the near term reduced collections could strain government finances. However, stronger demand is eventually seen making economic growth more sustainable, he said. Consumption heavy sectoral indices gained on Monday. Nifty Auto closed 4.18% higher, Niftyconsumer durables gained 3.38%, and Nifty Realty ended the day up 2.17%. "With external conditions volatile, government'sfocus is on strengthening internal demand which complements earlier tax cuts and lower interest rates," said Mehta. Reduction in GST slabs to two from four is seen supporting sectors such as insurance, consumer durables, auto and cement, said Aparna Shanker, chief investment officer, equity, at TheWealth Company Mutual Fund. The proposed changes to GST, however, could hurt demand in the short-run for the auto industry, other experts said. Uncertainty around when the new GST tax rates will be implemented may prompt customers to defer purchases, potentially affecting demand during regional festivals such as Ganesh Chaturthi in Maharashtra (end-August) and Onam in Kerala (late August to early September), said Kumar Rakesh, analyst-information technology and auto, BNP Paribas, in a report dated 18 August. Prolonged uncertainty could also lead to inventory challenges, as several manufacturers have begun building stock ahead of the festive period, he added. Monday, the NiftyMidcap index closed 1.9% up at 21,267.05 while NiftySmallcap rose 1.3% to 16,878.7. For Nifty 50, the zone of 24,800-24,770 is seen as a key support. On the upside, the 25,000-25,050 level will be a major hurdle, said SudeepShah, head-technical & derivatives research, SBI Securities.Any sustainable move above 25,050 will lead to a sharp upside rally up to the level of 25200, he added....