Communities minister Jake Berry said there was already a requirement in law to ensure changing places - but he was critical of the current provision in public places.
"There are only 12 motorway service stations out of nearly 100, only 50 out of nearly 500 shopping centres have them - that simply isn't good enough," he said.
Mr Cameron said that as chair of the Disability All Party Parliamentary Group she had heard "repeated distressing stories about disabled children being changed on toilet floors due to a lack of provision".
"It's unacceptable and also degrading in today's society" and asked the government to consider changing the law about suitable changing places.
Ceiling hoists needed
Mr Berry said there was already a requirement under the Equalities Act to ensure that changing places were provided and building regulations were currently under review. "I wouldn't wish to prejudice that," he said.
More than a quarter of a million severely disabled people do not have access to public toilet facilities that meet their needs, according to the campaign group, Changing Places.
Parents of severely disabled youngsters have long argued that they need disabled toilets to have an adult-sized changing bench, hoist and space for two carers, to save their children the indignity of being changed on often dirty toilet floors.
Changing Places would like to see appropriate facilities installed in public places, such as shopping centres, arts venues, hospitals, transport hubs, leisure complexes, sporting stadiums and arenas.