MEXICO CITY (Reuters) - Mexican leftist Andres Manuel Lopez Obrador has an 11-percentage point lead ahead of next year s presidential election, according to an opinion poll taken in the last week, giving him a sizeable advantage even after new rivals formally entered the race. The former Mexico City mayor Lopez Obrador has vowed to combat inequality and corruption, but some international investors are concerned about suggestions that he might reverse parts of the government s 2013-14 energy legislation. The poll, carried out and financed by Mexican public opinion firm Parametria, was provided exclusively to Reuters ahead of wider publication later on Tuesday. It was taken between Dec.14 and Dec.17. It found that 31 percent of those asked who they would vote for if the election were today would choose Lopez Obrador, followed by former Finance Minister Jose Antonio Meade, seeking nomination for the ruling Institutional Revolutionary Party (PRI), on 20 percent. Ricardo Anaya, former leader of the center-right National Action Party (PAN) was third on 19 percent, the poll said. Anaya resigned this month to pursue the presidency in an alliance with the center-left Party of the Democratic Revolution (PRD). The Parametria poll also included potential independent candidates, former first lady Margarita Zavala and Nuevo Leon Governor Jaime Rodriguez, giving them 10 percent and 2 percent respectively. Of the 800 people surveyed, 18 percent answered none of the listed candidates, did not know or did not reply. The Parametria poll is the first conducted since Lopez Obrador joined up with the conservative Social Encounter Party (PES), sparking worries among his progressive backers.  But the controversial alliance appears to have had little immediate effect on his advantage. The poll shows Lopez Obrador slightly further ahead than a survey by Mexican newspaper El Universal published in early December that gave him an eight-point lead. A survey by pollster Mitofsky, also from early December, showed a much closer race, with Lopez Obrador on 23 percent of the vote, followed by Anaya with 20 percent support and Meade with 19 percent.  Lopez Obrador unveiled his planned cabinet last week, including tapping a moderate U.S.-trained economist for finance minister and splitting the posts evenly between women and men.   The Parametria poll was conducted face-to-face and has a margin of error of 3.5 percentage points.  Mexican political parties have until March to formally register candidates. 