Labour party members opposed to a decision to have a women-only shortlist to choose their new MP from are expected to picket a selection meeting later.
The central Labour party in Wales is organising the selection
Blaenau Gwent MP Llew Smith is standing down at the next election and Welsh Labour leaders have insisted the local party select a female MP.
Some party members claim the all-women shortlist policy is undemocratic.
The constituency party decided to boycott the whole selection process, which is now being run by the Welsh Labour party centrally.
So far, 21 women have applied for selection which will be whittled down to about eight at Friday's meeting.
The final choice will take place in approximately three weeks' time.
Both Mr Smith and local assembly member Peter Law have been strong opponents of the policy.
The seat, which has been held by big party names Aneurin Bevan and Michael Foot, is one of Labour's strongest in Britain, and Mr Smith has a majority of almost 20,000.
The Welsh Labour executive has said it is implementing a policy backed by the party conference.
There is a similar women-only shortlist rule in Swansea East, where MP Donald Anderson is also standing down.