The ITF also failed to pull out of China, despite reiterating its call for the country to address Peng's claims she had been sexually assaulted by its former vice-premier, Zhang Gaoli.
Julian Knight MP, England's chairman of the Digital, Culture, Media & Sport select committee told Telegraph Sport: "This looks to the outside world like the ATP and ITF are gutless.
"This is a crucial moment for the sport, whether or not the dollar sign is more important than solidarity and integrity in the game. I hope that leading tennis players around the world will put pressure on the ATP and ITF to follow the example of the WTA."
Despite not joining the WTA's China boycott, Gaudenzi said Peng's plight had raised "serious concerns" and that the response to them had "fallen short".
"We again urge for a line of open direct communication between the player and the WTA in order to establish a clearer picture of her situation," he added.
"We will continue to consult with our members and monitor any developments as this issue evolves."
The ITF said: "Our primary concern remains Peng Shuai's wellbeing. The allegations Peng made must be addressed. We will continue to support all efforts being made to that end, both publicly and behind the scenes."
Knight also attacked the "lacklustre" response from the IOC to what has become a major diplomatic row after it announced it had held a second video call with her on Wednesday but made no mention of her sexual assault claims.
Tom Tugendhat MP, England's chairman of the Foreign Affairs select committee and the China Research Group, called on the Government to announce a diplomatic boycott of next year's Winter Games in Beijing.
"The WTA is right to stand up for the rights of athletes," he said. "I hope that the Government will follow this example and withhold any diplomatic representation from the 2022 Winter Olympics. Sport cannot be used to mask human rights abuses."
Peng's former doubles partner, Andrea Sestini Hlavackova, told Deutsche Welle it was "shocking" the IOC had not done more to ensure Peng was free to speak of her own accord.
She added: "It's really crazy to me that the IOC is putting it under the rug like, 'It's okay, she's fine', when they clearly know she's not."