New Zealand-born Ross passed away on 17 July
The New Zealand-born star's mother, Jude Harwood, made a formal complaint against the hospital on Friday. According to Jude, some of her son's medically trained visitors were unhappy that staff were using tap water to fill up the nebuliser he was using to breath, as opposed to sterile water.
Jude says that Ross's friends urged him to complain, although "sadly, he died before he could complain. He said they had used tap water all night."
In her letter Jude expressed concern that her son's treatment for leukaemia had weakened his immune system.
"Why weren't they checking the pipes? He was so vulnerable he didn't have a white cell in his body," she wrote.
Ross in 2003 with fellow chefs (L-R) Jean Christophe Novelli, Brian Turner and Ainsley Harriott
"I just don't want someone else to lose their son and die of Legionnaires disease when they could have come home."
TV stars and celebrity chefs were shocked to hear of Ross's passing in July, with many paying tribute to him on Twitter.
"Just heard the sad news my old Ready, Steady, Cook colleague Ross Burden has passed away," wrote Saturday Kitchen star James Martin. "My thoughts go out to friends and family. RIP Ross."
Ross's mother has made a formal complaint against the hospital
Ross, who returned to New Zealand to join the judging panel on the country's first MasterChef series in 2010, was remembered by his sister Kirsten as "a friendly, compassionate guy."
"He was my big, fantastic incredible, larger-than-life brother," she said shortly after his death. "Right up until probably a week-and-a-half ago, he was making his next lot of plans. He had the world mapped out."