Pharmac says a drug firm has campaigned to overturn its proposal to change key equipment used by diabetics.
The claim followed intense questioning of the Government's drug-buying agency by a Labour MP at Parliament's health select committee on Wednesday.
Pharmac is considering whether to proceed with a contentious plan to reduce the type of blood glucose meters and test strips it funds and to give the approximately $11 million contract to a sole supplier.
The agency told MPs that at present, it subsidises six types of meters and strips. It is considering changing to three supplied by one company as part of its regular work that enables it to stretch the drugs budget.
Labour's health spokesperson Maryan Street attacked the proposal, saying it is a backward step involving inferior technology and diabetics are worried.
Pharmac conceded that most feedback has been against the plan. It said all concerns are being addressed and no decision will be made for at least another month.
Outside the committee, Pharmac said drug firm Roche Diagnostics has written to politicians and others trying to engender concern.
Pharmac acting chief executive Steffan Crausaz says Roche Diagnostics would lose its $16 million contract if the plan goes ahead. Mr Crausaz says Pharmac cannot be influenced.
Roche did not respond to a request by Radio New Zealand for comment.