Both organisations want the Government to make it obligatory to maintain branches and have warned of the damage their closure could have on the disadvantaged.
The Irish Postmasters' Union is holding its Annual Conference in Mullingar in Co Westmeath this weekend.
Over the past five years, 500 post offices have closed, leaving about 1,200 offices around the country.
But the IPU says closures have taken place on an ad hoc basis and have resulted in an uneven spread of post offices.
It wants the Government to recognise the social value of post offices and to develop policy so that post offices can be kept open in more sparsely populated areas.
The call has been backed by the SVP. It says disadvantaged groups will be socially excluded unless the Government makes sure they have access to their local post office.
Audrey Dean, the society's policy officer, says the post office is not just about the provision of postal services.
