Critics of world football's governing body are spreading "fake news" and taking part in "Fifa bashing", says president Gianni Infantino.
Fifa's decision this week not to reappoint ethics chiefs Hans-Joachim Eckert and Cornel Borbely means an end to the reform process, the pair said.
Infantino's predecessor Sepp Blatter is serving a six-year ban from football for ethics breaches.
"We took over the organisation at its deepest point," said Infantino.
"We are rebuilding Fifa's reputation after all that happened."
Chief investigator Borbely and ethics adjudicator Eckert said "hundreds" of cases of alleged wrongdoing - some involving senior officials - were being looked into by Fifa's ethics committee before they were ousted.
In response to their claims, Fifa released a statement on Wednesday, saying it wanted to "better reflect the geographic and gender diversity that must be a part of an international organisation like Fifa".
"There are a lot of fake news and alternative facts about Fifa circulating," said Infantino, speaking before the Fifa congress in Bahrain.
"Fifa bashing has become a national sport in some countries. It was right but Fifa has changed now."
Last month, high-ranking Fifa official Sheikh Ahmad Al-Fahad Al-Sabah resigned a day after denying claims linking him to a fraud case. He denies any wrongdoing.
Infantino said the "new Fifa" under his leadership was a "transparent organisation" that was not "fiddling around".
He added: "If there is anyone who still thinks that he can enrich himself and he can abuse football, I have one plea for them - leave football now. We don't want you."
'Reform gurus failed miserably'
The governing body made a commitment to reform in 2011 after corruption allegations, only for a deeper scandal to emerge in 2015 that saw arrests and a raid at a hotel in Zurich as well as a large-scale investigation by US authorities.
Blatter and former Uefa boss Michel Platini were both banned after the former Fifa boss was found to have made a £1.3m "disloyal payment" to the Frenchman. Both men deny any wrongdoing.
French prosecutors are also investigating the bidding process for the 2018 and 2022 World Cups and have questioned Blatter.
Infantino was critical of governance experts who had been "paid millions" by Fifa to help reform the organisation, and claimed they had "rubber-stamped a sick and wrong system".
He asked: "Where were all these self-proclaimed gurus and experts? They all miserably failed. We will not accept good governance lessons from any individuals who miserably failed to protect football."
The former Uefa general secretary also offered "a big thanks" to authorities who had prosecuted officials involved in football corruption, saying they could "count on" Fifa's help.
'Nothing has changed from Blatter days'
However, ex-Fifa presidential candidate Prince Ali of Jordan said he believes nothing has changed under Infantino.
"This is the kind of congress that we have seen before," he told BBC Sport.
"The system, the way business is conducted, it is the same. I don't see the refreshing change, the openness, the transparency that everybody talks about taking effect on the ground.
"I feel a sense of responsibility to speak up when I see that things are not going right or when things are blatantly wrong. We can't keep saying the same thing."
What else did Infantino address?
- The need to boost women's football - he added that Fifa was looking at the creation of a 'world league' for the women's game, without giving further details
- Fifa's fight against racism, match-fixing and doping
- Fifa's finances - which he said were "extremely solid" after recent reports of major losses
- A charity match to be held between an England Legends and a World Legends team at Wembley when London hosts the Fifa Best Awards on 23 October
- Transfer regulations and agent fees
World Cup 2026 host revealed next year
The Fifa congress also voted overwhelmingly to fast-track the bidding process for the 2026 World Cup, which will be the first tournament expanded to feature 48 teams.
The winner will be announced in June 2018 at the governing body's annual meeting, which is due to take place in Moscow.
A joint submission from the US, Canada and Mexico remains the only declared bid, but a three-month window has now started for other nations to submit expressions of interest.
However, Europe and Asia are blocked under Fifa's rules from bidding because they will host the 2018 and 2022 editions of the tournament respectively.
Analysis - US, Mexico & Canada bid in pole position for 2026
BBC Radio 5 live sports news correspondent Richard Conway
Oceania lacks the interest and capability to host an expanded 48-team tournament and South America has already given its support to its northerly neighbours.
That leaves Africa. There are rumours of a potential bid by Morocco. However, that has not yet materialised and given the burden of having to stage 80 games it would be likely to require other adjoining countries to join them.
Such a bid would need huge infrastructure and stadium investment. Simply put, today's vote leaves US, Canada and Mexico in pole position to be awarded the tournament in one year's time.