A senior Roman Catholic has said voters in Democratic Republic of Congo should reject a draft constitution in next Sunday's vote.
The transitional team led by President Kabila has been in place for three years
A "No" vote would delay elections due next year under a deal ending DR Congo's five-year civil war.
A BBC correspondent in DR Congo says 55% of the population is Catholic and church leaders are seen as influential.
Pierre Anatole Matusila said the constitution had not been explained properly to the population.
"When I do not know what it is about, I say 'No'," said a statement released by Mr Matusila's Congress of Congolese Catholic laymen.
It added that the 'No' would be a sanction against the way politicians use lies and manipulation to rule the country.
The BBC's Arnaud Zajtman in the capital, Kinshasa, says Mr Matusila is an influential Catholic leader.
The head of the Catholic church, Archbishop Laurent Monsengwo, however, called on people to turn out and cast their votes in the 40,000 polling stations, without saying which way they should vote.
If passed, the constitution would set the rules for the elections due before the end of June 2006.
It would introduce a limit of two five-year terms for the president and the post of prime minister, named by the party with a majority in parliament.
Three years after the deal to end the war, a transitional government led by President Joseph Kabila and the former warring parties remains in power.
However, armed gangs continue to roam in much of the east, killing, looting and raping.
Some of the 15,000 UN troops in DR Congo have been helping the new Congolese army to flush out the rebel groups.