The US Open's decision to omit wheelchair competitions this year is "discrimination" and a "kick in the teeth", says reigning men's singles and doubles champion Andy Lapthorne.
On Wednesday, organisers said the Grand Slam would take place in New York from 31 August to 13 September, featuring men's and women's singles and doubles.
But it will not include mixed doubles, junior or wheelchair events.
"It's really tough to take," Britain's Lapthorne told BBC Sport.
The 29-year-old quad world number two said he had learned of the decision through social media and had had no direct communication from tournament organisers.
"We've had to battle for a lot over the years for what we've got right now," he said. "It just feels like we're going back years, and that's what hurts the most.
"To me, it's ableism. They've just used this as an excuse not to have the wheelchairs and they've not even consulted with the wheelchair guys to see whether they want to come and play. That's tough."
BBC Sport has contacted the US Open for comment.
The 2020 tournament, which will be held without fans, will be the first Grand Slam to take place since the coronavirus outbreak.
Lapthorne said he had spoken to former ATP world number one Andy Murray earlier on Wednesday, who had been a "great support" and had "restored his faith in tennis".
"It's just a bit of a kick in the teeth. I won there last year, I've earned the right to go and defend the title," he said.
"At the end of the day, we're earning a lot less money than the able-bodied guys, we rely on this money for us to be able to pay coaches, to be able to train and to be able to travel, to be able to live.
"They give this message that they want to be able to give players the opportunity to earn money and they've just neglected probably the most vulnerable group when it comes to prize money."
He added: "If you're going to open the doors to the top able-bodied players to play to then close the door on top wheelchair players because they have a disability, you've just assumed they won't come and play because of the current climate.
"To me, that is backward thinking. They need to realise that this is my job, this is how I gain an income, this is how I support my family, this is how I do everything with my life.
"The only word you can use to describe it is discrimination."
In a statement, the International Tennis Federation (ITF) said it "understands and shares the disappointment felt by many".
"We fully appreciate the huge logistical challenges faced by organisers in what are unprecedented times. It is right that in the midst of a global pandemic, the safety of all competitors must be the first and only priority," the federation added.
"We continue to discuss with the organisers potential approaches that could allow the wheelchair tennis competition to take place either on or off site."
Earlier on Thursday, Australian quad world number one and Paralympic champion Dylan Alcott said the US Open's decision was "disgusting discrimination", while Britain's Gordon Reid, the Paralympic wheelchair men's singles champion, said he was "massively disappointed".
However, British women's wheelchair singles player Jordanne Whiley said on Instagram she didn't think it was a "intentional, direct act of discrimination".
"Having said that, I don't think their decision was a right one," she added. "By doing what they've done, they've sent a message to the world that says 'we don't think you're as important or as valued or as respected as the able-bodied players' that we would like to play at our event."
International Paralympic Committee (IPC) president Andrew Parsons has urged the US Open to reconsider its decision.
An IPC statement said: "The International Paralympic Committee is disappointed at the US Open's decision not to include wheelchair tennis in this September's event, a decision that has left a lot of the athlete community rightly upset and angered.
"We urge organisers to reconsider this decision which could potentially undo years of great work to promote and showcase the sport of wheelchair tennis."