Labour has been accused by one of its MPs of trying to impose "puppets" on local parties after opting for all-women shortlists in two south Wales seats.
Llew Smith says the decision is an insult to his party
The Blaenau Gwent branch promised to fight the decision after the Wales Labour Party decided that only women should be allowed to enter the race to succeed its MP.
Swansea East has also been told it must have an all-women shortlist, but Bridgend has been told it can choose a man if it wants.
These are the three Welsh seats where the sitting MPs have announced they will retire.
The ruling by the Wales Labour Party has led to claims of New Labour control-freakery.
If they want a fight
they're going to get one
But Labour said the decision had been taken to solely to improve Wales' poor record on women MPs.
Blaenau Gwent MP Llew Smith, who will stand down at the next general election, said it was a "disgrace".
"This is nothing about gender balance, it's
about politics," he said.
Mr Smith's predecessors in the seat include NHS founder Aneurin Bevan and former Labour leader Michael Foot.
Blaenau Gwent has had Nye Bevan and Michael Foot as MPs
"It's about the determination of senior bureaucrats in the Labour party in
Wales to trample on the traditions of the Nye Bevans and Michael Foots of this
world, and their determination to ensure that my successor doesn't come from the
socialist wing of the party," he said.
"What they want is someone from New Labour who will act like a puppet."
He said Labour had insulted his constituents.
"We do not intend to sit back and accept this decision," Mr Smith said. "We
will fight it up and to and after the election if needs be. If they want a fight
they're going to get one."
Blaenau Gwent constituency secretary Dai Davies said: "I think it will be very very difficult for the constituency ever to accept the imposition of a candidate.
Women are 50% of the population, yet just 10% of Welsh MPs are female
"I make it quite clear that we are not against women candidates, women in politics, women in our wards and constituency.
"What we are against is the party at a higher level trying to impose a candidate in our constituency."
Mr Davies said the move would cause "untold damage" and would "only serve to drive people away from the party".
But Preseli Pembrokeshire MP Jackie Lawrence said Wales had the worst record on representation at Westminster in the UK, with only 10% of women MPs, against a countrywide average of 18%.
It's very very sad if Blaenau Gwent do decide to fight against this decision," she said.
There are only four women Welsh Labour MPs, and three of those are in marginal seats. Jackie Lawrence said women should be candidates in solid Labour areas.
By contrast with Westminster, Wales has the best record in the world on electing female members of its assembly.
Half of the 60 members chosen at the election last month were female - the first time that has happened in a national body.
A Welsh Labour spokeswoman denied the move was political, saying it had been
taken purely to improve women's representation.
"Wales has the worst record in Britain on women MPs and we have to take
measures to redress the balance," she said.
"Women are 50% of the population, yet just 10% of Welsh MPs are female. We
are determined to improve on our record."