The disruptions may threaten the ballot less than three weeks before it is due to be held, a top electoral official warned on Wednesday.
National Electoral Council Vice-president Ezequiel Zamora, one of five directors, urged authorities to keep the schedule for the 15 August, which international observers hope will end simmering conflict in the world's fifth largest oil exporter.
"We must go at full speed. I am not accusing anyone ... but I feel we are getting close to a delay," Zamora told reporters.
"We would be playing with Venezuela's peace if anybody were crazy enough to change the 15 August date."
The referendum is the latest challenge to Chavez, a former army officer who was elected in 1998 vowing to battle poverty.
Critics say he has become increasingly authoritarian in the face of fierce opposition to his self-style revolution.
Opposition leaders say they want to know why thousands of voters have had their assigned election centres changed without explanation.
"We would be playing with Venezuela's peace if anybody were crazy enough to change the 15 August date"
National Electoral Council VP
They have also denounced inconsistencies in the electoral register and a move by the council to dismiss polling station workers who signed an opposition vote petition last year.
"These abuses such as the fraudulent transfer of voters are all about the game of sabotage the national electoral council is playing," opposition leader Antonio Ledezma said.
Most observers say three of the electoral council's five top directors side with the government and two are in favour of the opposition.
Electoral council president Francisco Carrasquero has denied any fraud in the electoral register and officials say they will iron out any inconsistencies this week. Nearly 14 million people are registered to vote.
"I don't see any major obstacles," said council director Jorge Rodriguez.
An international mission set up by the Organization of American States and former US President Jimmy Carter hammered out an accord for the referendum a year ago.
Venezuela has been rocked by confrontation for more than two years, including a coup, an oil strike and months of protests.