The member charities, which provide support services to victims of crime, voted by nine to one in favour of the merger at an extraordinary general meeting in London on Saturday.
Government funding, which accounts for three quarters of Victim Support income, has been frozen at £30m for three years. According to a Victim Support spokesman, the Government told the charity that that sum would not be increased until the charity could supply a clearer picture of what it was doing with the money.
The spokesman said: "There was a National Audit Office investigation a few years ago and although we came out of it fine, the Government was told they needed more robust facts and figures about what we were doing with their money. But we were finding it very difficult to provide that with the federal structure."
The spokesman said a number of long-standing internal factors had also been "every bit as important" in the merger decision, such as a desire to minimise "duplication of effort" and to speed up decision-making, which currently can take up to a year.
Chief executive Gillian Guy said: "As a single national charity we will have greater focus, be more responsive to changes and opportunities in the environment, and make better use of our pooled resources."
The charity also hopes the merger will also improve its bid to deliver the ‘enhanced services' for victims of crime mooted in the 2005 Green Paper Rebuilding lives: supporting victims of crime.
It had already begun "restructuring" at its national office in anticipation of the merger, a process that will see its 90 staff there reduced to 40. The spokesman said: "Delivering services and managing them nationally requires a different skill set and structure."
Victim Support, which has around 9,000 volunteers working in the community and in courts, began as a single charity operating in the Bristol area in 1974. Its 300 local schemes merged in the late 1990s to form the current federation of almost 90 separate charities.
Those charities will now dissolve and merge with the national body, which will adopt a new Memorandum and Articles of Association. The charity hopes the process will by complete by July 2008.