Campaigners are to urge MPs to join their push to secure a right to a break for carers of disabled children.
Carers are close to breaking point, campaigners say
Every Disabled Child Matters - a consortium of four charities - will meet MPs later to try to win their support for a private member's bill.
The bill calls for the NHS and local authorities to provide each carer with access to a review to determine what level of break they should get.
At the moment some councils provide breaks but it varies from area to area.
The campaign said there were 100,000 families in England providing substantial care to disabled children.
Research has suggested eight out of 10 are close to breaking point because of a lack of support.
Surveys have also found that a third of areas are cutting their short-break provision.
The bill, which will need to be presented to Parliament by either a peer or MP, proposes amending the Children's Act 1989 and the Childcare Act 2006.
The campaigners are calling for local authorities to provide assessments of carers to see how much support they need.
Mencap, part of the Every Disabled Child Matters group, recommends 52 night breaks a year - one per week - for families of children with multiple learning and physical disabilities.
Mencap chief executive Jo Williams said: "At present the delivery of the government's strategy towards disabled children and their families is dire.
"We need proper funding to ensure the system is fully transformed so that people can access short-break care when and where they need it."
The campaign estimates a minimum of £150m extra each year will be needed to pay for the entitlement, but said it has already received support from 50 MPs.
Francine Bates, chief executive of Contact a Family, another member of the Every Disabled Child Matters group, said: "Given the amount of parliamentary support we have had for the campaign, and the fact that so many families across the country are desperate for a break, we are confident that we will get a large number of MPs offering to take up this bill."