In an open letter sent to PGA Tour commissioner Jay Monahan, eight-time major champion Watson said the bombshell agreement announced on June 6 had been brokered "without due process."
The former US Ryder Cup captain posed a series of questions to Monahan in the letter while asking whether the merger was driven by financial necessity.
"What does acceptance of this partnership mean to the Tour? What do we get? What do we give up?" Watson asked.
"Why was this deal done in such secrecy and why wasn't even one of the players who sits on the Tour's Policy Board included?"
Under the deal announced earlier this month, the PGA Tour and DP World Tour have joined forces with Saudi Arabia's Public Investment Fund (PIF), which has bankrolled the upstart LIV Golf circuit.
Watson acknowledged that the rise of LIV Golf had threatened the PGA Tour's business model, while creating "unprecedented obstacles and battles of both moral and financial consequence."
Watson asked whether the tie-up with Saudi's PIF - a government controlled fund which reportedly manages assets worth $650 billion - was the only way to ensure the PGA Tour's long-term survival.
"Is the PIF the only viable rescue from the Tour's financial problems? Was/is there a plan B?" Watson asked.
"And again, what exactly is the exchange? We need clarity and deserve full disclosure as to the financial health of the PGA Tour and the details of this proposed partnership."
Watson also fired a broadside at the "hypocrisy" of the PGA Tour in embracing LIV's Saudi backers.
Monahan last year invoked the September 11, 2001 attacks on New York and Washington when urging PGA Tour players not to join LIV. Fifteen of the 19 hijackers on 9/11 were Saudi citizens, and Monahan's abrupt U-turn has been slammed by families of victims of the attacks.
"I ask the tour, how is a non-negotiable point for us one day one we negotiate around the next?" Watson asked in the letter, referring to 9/11.
"My loyalty to golf and this country live in the same place and have held equal and significant weight with me over my lifetime," Watson added.
"Please educate me and others in a way that allows loyalty to both and in a way that makes it easy to look 9/11 families in the eye and ourselves in the mirror."
