CNRP leaders Sam Rainsy and Kem Sokha announced the planned demonstrations at a press conference at party headquarters in Phnom Penh on Sunday afternoon.
Mr Rainsy said there would be a series of demonstrations and they would be larger than the opposition rally last Saturday.
He said the rallies would last for at least three days.
“It could take a variety of forms, the form of a meeting, the form of a sit-in or the form of marches,” Mr. Rainsy said, adding that specifics about the demonstrations would be determined over the coming week.
The NEC announced the final election results on national TV and radio, confirming that Mr. Hun Sen’s CPP won 68 National Assembly seats to 55 for the CNRP.
The results are identical to those that were announced by CPP Information Minister Khieu Kanharith on the evening of the July 28 vote.
In the weeks following the election, the NEC, which claimed there was a lack of evidence, dismissed dozens of complaints issued by the CNRP over alleged election irregularities.
The Constitutional Council of Cambodia on Friday wrapped up its review of the disputed results saying that none of the CNRP’s complaints merited a wider investigation, though it did order the NEC to seek punitive action against local election officials responsible for minor irregularities.