Catalonia\'s leader Artur Mas said Sunday he will have to share power as he fights for greater sovereignty for the rich Spanish region after voters slashed his majority. Mas\'s majority in the regional parliament fell in favour of leftist parties which, like him, favour a referendum on self-rule, official results showed after Sunday\'s vote. \"From this result we note that we are clearly the only force that can lead this government, but we cannot lead it alone. We need shared responsibility,\" Mas told supporters in Barcelona. \"There must be a period of reflection in Catalonia over the coming days. The presidency must be taken up, but we will also have to reflect along with other (political) forces,\" he said, without naming a particular party. Mas\'s centre-right CiU alliance saw its parliamentary presence fall to 50 seats from 62 in the 135-seat parliament. Leftist pro-independence party ERC came second with 21, results from the regional government showed, with 97 percent of votes counted. Mas had vowed to hold a referendum on \"self-determination\" if Sunday\'s vote gave him a strong mandate. ERC seeks independence for Catalonia from Spain, but has sharply different political objectives from CiU.