The commission said "e-counting" in the recent election had worked well in a number of areas, adding that where counts have been completed, the results are accurate and final.
But it said "serious technical failures have arisen to delay the announcement of results" in various areas, adding: "We share the public's concern about the high number of rejected ballot papers." According to a BBC report, seven vote counts were suspended and up to 100,000 ballot papers were spoiled.
Behavioral psychologist Catriona Campbell said the voting process was also too complicated.
Campbell, who runs usability consultancy Foviance, said voters had difficulty with two separate ballots.
"No one explained the process, so voters were rating all 10 candidates when they only needed to rate the candidates they actually wanted to vote for, which slowed up proceedings," she said. "Some voters rated two candidates in the same party as their first choice, which meant their ballot paper was officially spoiled."
Julian Goldsmith of Silicon.com reported from London.