The Ulster Unionist Party (UUP) has described radical plans to enhance cross-Border economic and infrastructural co-operation as an attempt to make the North "an economic colony of the Irish Republic".
The SDLP and Sinn Féin welcomed the proposals in the Comprehensive Study Of An All-Island Economy, but UUP deputy leader Danny Kennedy said the document "looks like it was written by a Sinn Féin policy officer".
He said: "The UUP is all in favour of mutual economic co-operation and trade between the two states.
"However, this document is a different proposition entirely. It seeks to create a Northern Ireland that is a region or an economic colony of the Republic as opposed to a Northern Ireland that is a trading partner with the Republic but which forms part of the United Kingdom's economic bloc."
He acknowledged that some infrastructure proposals have merit but said the language in the document appeared to be intended to "put the frighteners on people as to what plan B could look like in the absence of a power-sharing deal".
Parties in the North have been given until November 24 thto agree to restore power-sharing with a view to in late March. The governments have threatened to impose an alternative which would see a role for Dublin in the affairs for Northern Ireland.
UUP leader Sir Reg Empey said he was particularly concerned that cross-Border trade missions abroad would neuter Invest NI. "The fact is, we are in competition, particularly with our fiscal regime not being the same," Sir Reg said.
But SDLP deputy leader Alasdair McDonnell welcomed the document and said unionists had nothing to fear from it.
"It is absolutely nonsensical that there should be an economic boom in Dublin and a hundred miles away in Belfast there is economic stagnation," Mr McDonnell said."
Sinn Féin economic spokesman Mitchel McLaughlin said the document reflected his party's position and urged the governments' match their "rhetoric" with action.
Additional reporting PA