The Cystic Fibrosis Trust fears charity lotteries will fall by the wayside unless the Government amends the Gambling Bill to allow them to offer £1m prizes.
In a letter to The Guardian, Rosie Barnes, the trust's chief executive, said the Government had refused to consider the amendment.
She added that although charity lotteries were fully engaged in the Bill's scrutiny process, they had been "pushed to the margins behind the pizzazz and lobbying clout of Las Vegas casino operators".
Barnes said she feared the provision of charitable purposes was unlikely to be catered for by large gambling operators. She asked: "Will MGM Mirage, Caesars et al take up the mantle of providing scout huts, hospice care and sports clubs when charity lotteries are frustrated?"
Rather than helping charity lotteries, she said, the Bill "allows the proliferation of internet gambling and lottery scams".
The Bill began its progress through a Lords committee last week.
Barnes refused to discuss her letter further with Third Sector.