World Rugby's board on Tuesday recommended that South Africa host the event, placing France in second position and Ireland in third ahead of the decisive vote by the governing body's council on Nov. 15.
"We wrote to (World Rugby chairman) Bill Beaumont to point out several blatant errors," Laporte told Reuters on Friday.
"I don't believe in bad faith. I rather think that it's incompetence."
A spokesman for World Rugby said that the governing body was unable to comment on the matter.
South Africa received an overall score of 78.97 percent in the report to 75.88 for France and 72.25 for Ireland on a selection of weighted criteria.
"How come we are less well marked than South Africa on hotels? They're saying there are not enough hotel rooms in St Etienne. They hosted Euro 2016 matches, there are 1,500 rooms there. It's nonsense," the former Toulon and France coach said.
Laporte also said that the evaluation was carried out mostly by World Rugby employees and "not by two auditing firms as it was supposed to be". "We are not happy about that," he said.
South Africa earned better marks than France on stadium plans. South Africa benefits from facilities from the 2010 soccer World Cup, but Laporte said that France was also well-served, having staged the European soccer championship last year.
"They're saying we don't own the stadiums. Of course we don't own them, but the cities and the French football league have committed to freeing the stadiums for the World Cup, yet they (World Rugby) say the are not so sure," said Laporte, who also noted that the French federation's total financial return would be 536 million pounds ($700.39 million) -- 64 million more than South Africa's.
Laporte was also frustrated that France was criticised for its anti-doping policies.
The evaluation report said there was "some element of risk" because under French law it is illegal to use, hold or sell narcotics.
"That's laughable. We're less well marked because we're too tough on doping," said Laporte, who is confident France can still convince enough people to vote for his country on Nov. 15.
"The match has not begun yet," he said. "And even Ireland are still in the competition. It is not up to World Rugby employees to decide who hosts the World Cup. It's up to the federation presidents."
The South African, French and Irish federations will not take part in the vote.
($1 = 0.7653 pounds)
(Reporting by Julien Pretot; Editing by Toby Davis)
