CARACAS, July 24 (Reuters) - Venezuelan president Nicolas Maduro’s attempt to use Latin hit “Despacito” - which means ‘slowly’ - to inject some cool into his controversial new congress has backfired quickly.

Maduro’s unpopular leftist government on Sunday promoted a remixed version of “Despacito” to encourage Venezuelans to vote for the Constituent Assembly, which will have powers to rewrite the national charter and supersede other institutions.

“Our call to the ‘Constituent Assembly’ only seeks to unite the country ... Despacito!” goes the Socialist Party-sanctioned remix of the catchy dance song, which was played during Maduro’s weekly televised show.

“What do you think, eh? Is this video approved?” a grinning and clapping Maduro called out to the crowd, which roared back in approval.

But Puerto Rican singers Luis Fonsi and Daddy Yankee on Monday said they do not approve at all.

“At no point was I asked, nor did I authorize, the use or the change in lyrics of “Despacito” for political ambitions, and much less in the middle of a deplorable situation that Venezuela, a country I love so much, is living,” Fonsi said in a message posted on Twitter.

Daddy Yankee, meanwhile, posted a picture of Maduro with a big red cross over it on Instagram.

“That you illegally appropriate a song (Despacito) does not compare with the crimes you commit and have committed in Venezuela. Your dictatorial regime is a joke, not only for my Venezuelan brothers, but for the entire world,” he said.

“With this nefarious marketing plan, you only highlight your fascist ideal.”

Millions of Venezuelans have been staging months of protests against Maduro, a former bus driver and union leader narrowly elected to replace the late Hugo Chavez in 2013.

Some 100 people have died in the unrest, which has further hammered an imploding economy that is running short of food and medicine.

Critics say Maduro is trying to cement a dictatorship by pushing forward with the Constituent Assembly this Sunday. He says it is the only way to bring peace back to the convulsed nation.