Peter Law defeated Labour's Maggie Jones in Blaenau Gwent

Mr Law beat Labour candidate Maggie Jones in Blaenau Gwent in the recent general election.

He stood as an independent in protest against an all-women shortlist which Labour imposed in the constituency.

Labour chairman Ian McCartney said the 20 members appeared to have acted in a way to lead to automatic exclusion.

After a meeting on Tuesday, Mr McCartney said they would be thrown out unless they can prove the facts were wrong.

They are looking for scapegoats for what went wrong Elena Evans

"They will be written to and, unless the members concerned dispute the facts (claiming for instance that they never agreed to appear on Peter Law's leaflet as a supporter), they will automatically be excluded from party membership," he said

But the left-wing NEC member Mark Seddon said eight of the 20 had no idea why they were facing disciplinary action.

Elena Evans, from the neighbouring constituency of Islwyn, said she believes she is facing expulsion for a letter she wrote to a newspaper.

She said her reaction is "one of disbelief".

"They are looking for scapegoats for what went wrong," she said.

Before the election, Blaenau Gwent was Labour's safest seat in Wales, and Mr Law overturned its majority of 19,000 to win by more than 9,000 votes.

Before the NEC meeting, defeated candidate Ms Jones, who is a member of the NEC, defended the use of all-women shortlists and supported the expulsions.

We can't have a different rule for Blaenau Gwent Maggie Jones

"The fact is that this decision, all-women shortlists, was a democratic decision by the Labour Party conference," she said.

"It is something that the grassroots members fought for many, many years.

"There is nothing in Blaenau Gwent that was any different from any other seat and the reason we are doing it is not for some bureaucratic reason.

"At the end of the day we have got to keep faith with the Labour Party membership who made the decision that there should be all-women shortlists.

"We can't have a different rule for Blaenau Gwent."

Mr Law, who is also the AM for Blaenau Gwent, has expressed surprise and disappointment at the potential expulsions.

Welsh Secretary Peter Hain said there was no "witch hunt" against Mr Law or "vendetta" against his supporters.