There were fears that a private company could be awarded the contract for the service after cutbacks at the Post Office in recent months.
However DUP man Mr Campbell said said that the right decision has finally been made.
"It is my belief that the Post Office was best placed to provide this service, particularly in rural areas such as Northern Ireland," he said.
"A large number of constituents had contacted me regarding retaining the Post Office Card Account with the Post Office and this was backed by MP's across all Parties at Westminster who supported a Motion in The House of Commons.
"I am pleased that the Department of Work and Pensions has recognized the value of this service remaining within Post Offices.
"Over the last few months Post Office closures have hit many areas across the UK including my own constituency.
"If the Post Office Card Account service had been removed it would inevitably have lead to further closures which would have caused maximum impact on the most vulnerable in our society including
the elderly and those who need to access benefits.
"The Government's announcement is welcome however they need to do more to safeguard the future of our Post Offices.
"The range of services needs to be expanded to increase the numbers of people visiting their local Post Office on a more regular basis to secure a long term future for our Post Offices throughout Northern Ireland."