Members of the Long Term Conditions Alliance were this week set to agree to merge with a new patient representation body.
The alliance is expected to become part of National Voices, being developed by its chief executive, David Pink.
National Voices, which has secured government start-up funding, will be an umbrella body representing interest groups, charities and policy makers. It has around 20 member organisations but Mr Pink said he hoped this would reach 250 by the spring. The alliance's board is supporting the merger, with an announcement due this week.
Mr Pink said the change would mean National Voices taking on substantial staff and resources. The alliance was ready to become part of the larger organisation because of the raised profile of long-term conditions, he added.
"We are comfortable that long term conditions will remain a priority within that organisation," he said.