The Institute for Access to Federal Information, or IFAI, urged Mexico's four presidential candidates to "boost transparency and accountability and make them a part of Mexicans' political culture."

Over the past decade, since a transparency law and its implementing mechanisms were enacted during the administration of former President Vicente Fox, steps have had to be taken to "overcome resistance and attempts at regression by authorities who don't understand that there's no turning back," IFAI's president-commissioner, Jacqueline Peschard, said in a statement.

The IFAI sent four letters to the presidential hopefuls on the 10th anniversary of the enactment of the Federal Law on Transparency and Access to Public Government Information, urging them to champion that legislation as "one of contemporary Mexico's most important and transcendent democratic advances," Peschard said.

"We can't agree more that both (transparency and accountability) are essential elements in a democratic government. That is why they must be strengthened and made part of Mexicans' political culture," the IFAI official said.

The letters were sent to Josefina Vazquez Mota, of the governing conservative National Action Party, or PAN; Enrique Peña Nieto, of the main opposition Institutional Revolutionary Party, or PRI; Andres Manuel Lopez Obrador, candidate of the left-wing Party of the Democratic Revolution, or PRD, the Workers Party, or PT, and the Citizens Movement; and Gabriel Quadri, of the New Alliance Party, or PANAL.

Peña Nieto is the frontrunner and until recently had enjoyed a big lead in voter-preference surveys. One poll released last Thursday, however, showed Lopez Obrador had narrowed the gap to just four percentage points.

Mexico will hold its presidential election on July 1, selecting a successor to President Felipe Calderon, who is constitutionally limited to a single six-year term.

Calderon defeated Lopez Obrador in the 2006 presidential contest by the narrowest margin in Mexican history, a mere 0.56 percent of the 41 million ballots cast.

Claiming fraud, Lopez Obrador demanded a full recount, but election authorities agreed to review only a small percentage of the ballots and the top electoral court proclaimed Calderon the winner, even though judges acknowledged that PAN incumbent Fox's efforts on behalf of his party colleague had violated the law.

Nearly 80 million Mexicans will be eligible to vote for a new president, 628 legislators and thousands of other officials in the general elections. EFE