LONDON, Jan 18 (Reuters) - British energy market regulator Ofgem said on Tuesday that Together Energy Retail has ceased to trade, the latest power supplier to be driven into financial difficulty by a surge in wholesale gas and electricity prices. More than 20 energy suppliers have collapsed since the beginning of September due to spiralling wholesale power and gas costs and because the regulator Ofgem"s price cap prevented them passing on rising costs to customers. The number of companies supplying gas and electricity to British homes more than halved last year. The company supplies around 176,000 domestic customers and one non-domestic customer. Ofgem said customers" energy supply will continue and the funds paid into accounts will be protected, where they are in credit. "In recent weeks there has been an unprecedented increase in global gas prices which is putting financial pressure on suppliers. Ofgem is working closely with government and industry to make sure customers continue to be protected this winter," the regulator said.