The DUP has warned the proposed re-drawing of electoral boundaries could have "far-reaching and negative" political consequences.
As part of an overall reduction in the number of MPs, from 650 to 600, Northern Ireland's total would drop from 18 to 17.
The four current Belfast constituencies could merge into three, with the DUP projected to lose a seat to Sinn Féin.
A spokesperson for the DUP said the reforms would "produce an unrepresentative political result" that would have, "the potential to have far-reaching and negative political consequences for the constitutional stability of Northern Ireland.
"The end result of this flawed approach is an unnecessary level of change and constituencies that make statistical sense but very little else."
Under the plans, East Belfast would remain largely untouched, with two new seats comprising the rest of the city being created- Belfast South West and Belfast North
The Boundary Commission who are overseeing the upheaval say they have not taken party political considerations into account and cannot predict weather unionists or nationalists would emerge as winners or losers.
As the number of seats at the Northern Ireland Assembly are linked to Westminster representation, Stormont would also shrink.
Under the current system of five members per constituency, the number would drop from 90 to 85.
Sinn Féin have yet to comment on the proposals.
The SDLP criticised the plans for Belfast, saying, "The proposed reduction in representation would inevitably lead to a diminution in the standing and influence of Belfast as a major city and regional capital.
"We believe that this would sit at odds with the natural progression and development of cities and regions."
Elsewhere in Northern Ireland, proposed constituency boundary changes would see some demographic shifts in seats.
The seat presently known as Fermanagh South Tyrone has long been a marginal constituency but would likely have a sizeable Sinn Féin majority under suggested reforms.
In 2011, MPs voted for the constituency boundary review as part of plans to reduce costs and in a bid to bring boundaries in line with fluctuating community changes such the expansions of some cities.
The consultation period on proposals is due to end in October. The final boundary proposals will be put to the House of Commons for approval before being implemented.