* Chavez says would be "ashamed" to debate Capriles
* Opposition candidate chides presidents for insults
* President retains double-digit lead in poll
CARACAS, June 18 (Reuters) - Venezuela's President Hugo Chavez ruled out on Monday holding a pre-election debate with opponent Henrique Capriles, saying he would be "ashamed" to measure himself against such a "non-entity."
Stepping up the rhetoric in the polarized South American nation's run-up to the Oct. 7 vote, Capriles replied that Venezuelans were tired of the socialist leader's stream of insults.
Battling a recurrence of cancer that has kept him off the street, Chavez, 57, leads most major opinion polls by a double-digit margin and officials are exuding confidence of a comfortable re-election win.
Capriles' camp, though, insists some polls are skewed, many Venezuelans are scared of expressing their real opinions, and their grassroots campaigning is beginning to make headway.
Asked at a news conference if he would be prepared to debate Capriles, Chavez replied: "I'd be ashamed because what you have there is nothing ... I'd have liked to face a heavyweight, not a non-entity."
Since Capriles, a center-left young state governor, won the opposition coalition's primary in February, Chavez has not mentioned him by name, preferring to use a stream of insults including "pig" and "loser".
Capriles has sought to focus his campaign on Venezuelans' daily problems - crime, unemployment and stuttering social services - rather than be drawn into a rhetorical fight.
Yet he responded sharply on Monday to Chavez's latest salvo.
"The candidate of backwardness could never debate with anyone, he only knows how to insult and discredit people - a worn-out and tedious speech," he said via Twitter.
LATEST POLL GIVES CHAVEZ 17-POINT LEAD
Capriles also mocked the president's comments this week about seeking to send a second Venezuelan satellite into space with Chinese help, saying he should first resolve more pressing issues of ill-equipped hospitals and crime.
"Will our people's problems be resolved putting a satellite into orbit? Will they do away with violence from outer space?"
The latest opinion poll, published by local company Hinterlaces on Monday, gave Chavez 51 percent of voter intentions versus 34 percent for Capriles.
Though that was a fall by two percentage points for Chavez from his showing in the same pollster last month, it still represented a formidable gap for the opposition.
Chavez appears to have won considerable sympathy for his cancer, while his popularity among the poor remains high due to heavy spending on welfare projects and his personal charisma.
Despite his cancer treatment, the president has been increasingly active in the last two weeks, appearing more frequently on state media and attending several events in person. He addressed Monday's news conference of the ruling Socialist Party by telephone, however.
Capriles, who by contrast projects an image of youth and energy, is drawing large crowds on his daily visits to remote corners of Venezuela and is promising a Brazilian-style "modern left" government should he unseat Chavez. (Editing by Philip Barbara)