Mr Warner, who said he feared for his life, also said he could link Fifa officials to general elections in his native Trinidad and Tobago in 2010.
He is one of the 14 people charged by the US over alleged corruption at Fifa.
Another top Fifa official and key witness, American Chuck Blazer, has admitted accepting bribes.
The admissions came in a newly released transcript of Mr Blazer’s guilty plea from 2013, as part of a wide-ranging US criminal case that has engulfed Fifa and led president Sepp Blatter to resign.
The US justice department alleges the 14 people charged worldwide accepted bribes and kickbacks estimated at more than $150m (£97m) over a 24-year period. Four others have already been charged, including Mr Blazer.
Accused of racketeering, wire fraud, money laundering, bribery
From the early 1990s, he allegedly “began to leverage his influence and exploit his official positions for personal gain”
Allegedly accepted a $10m bribe from South African officials in return for voting to award them the 2010 World Cup
Allegedly bribed officials with envelopes each containing $40,000 in cash; when one demurred, he allegedly said: “There are some people here who think they are more pious than thou. If you’re pious, open a church, friends. Our business is our business”
Mr Warner, 72, resigned from all football activity in 2011 amid bribery allegations and later stepped down as Trinidad and Tobago’s security minister amid a fraud inquiry.
A key figure in the deepening scandal, he said he had given lawyers documents outlining the links between Fifa, its funding, himself and the 2010 election in Trinidad and Tobago. He said the transactions also included Mr Blatter.
“I will no longer keep secrets for them who actively seek to destroy the country,” he said in an address on Trinidadian TV on Wednesday evening entitled “The gloves are off”.
Speaking to his supporters at a rally later the same day, he promised an “avalanche” of revelations to come.