A trade union has been accused of trying to "stitch up" Labour's selection contest to replace disgraced MP Eric Joyce.

Labour members in Falkirk received a "survey" last week on whether an all-woman shortlist (AWS) should be used for the safe seat.

Unite, a union that is backing left-winger Karie Murphy to stand for the vacancy, is paying for the survey.

Murphy, the office manager of high-profile Labour MP Tom Watson, stands to benefit from a female-only panel of candidates.

Joyce pled guilty to assault last year after attacking four people in a House of Commons bar.

His subsequent resignation from Labour means the party has to select a new candidate for Falkirk, which Joyce won in 2010 with a 7843 majority.

The contenders for the imminent selection contest also include former Falkirk Council leader Linda Gow and Gregor Poynton, the UK political director at communications firm Blue State Digital.

According to a report produced by an internal grouping inside Unite, the union is "very likely" to back Murphy and has recruited "well over 100 Unite members" to the local constituency.

A separate Unite leaflet states the union has "asked Karie Murphy to consider standing for selection" and contains an endorsement of the candidate from Unite general secretary, Len McCluskey.

However, a row has broken out over whether Unite is trying to nudge Labour towards an AWS, an outcome that would knock Poynton out of the race and therefore benefit Murphy.

The "consultative survey", produced by the Falkirk West constituency party, asked: "Do you agree that Falkirk would benefit from an 'All Woman Shortlist' for the Westminster selection?"

The freepost envelope that comes with the survey has fuelled suspicions, as the address for responses is Unite's London headquarters.

The name on the envelope is Stephen Deans, who is chairman of the local constituency party and chairman of Unite in Scotland.

The "do you agree...?" formula in the survey question has also irked some local members.

When the SNP Government proposed the same phrase for its independence referendum, Labour MP and Better Together leader Alistair Darling dismissed the wording as "loaded".

One Labour source said: "Members are furious about this survey, which is clearly aimed at helping one individual get the nomination. It is being seen as an attempt to manipulate the process."

A second Labour insider said: "The fact that this survey has to be sent back to London will be very concerning for local members. This looks like a stitch-up."

The survey has now prompted Gow and Poynton to write to local members about the issue, saying: "We are taking the highly unusual step of two opponents putting themselves forward for selection in writing to you jointly about a matter about which we feel incredibly strongly.

"We strongly believe all Falkirk members regardless of gender should have the opportunity to put themselves forward for selection.

"To have an AWS here after the past problems of the CLP [Constituency Labour Party] is the wrong decision, at the wrong time."

Speaking to the Sunday Herald, Deans said the local party had approved a survey and Unite had "kindly agreed" to pay for it.

He added that the results would be considered and collated in Scotland. "A report will be compiled, and it then goes to the organisation sub-committee from the acting general secretary of the Scottish Labour party," he said.

Asked whether Unite, by paying for the survey, was trying to help Murphy, he said: "It doesn't surprise me that some people may say that, but they are saying that for all the wrong reasons.

"Unite is in the process of developing a constituency development plan, which involves finance for the constituency party."

A decision on whether an AWS will be used in Falkirk and other seats is expected to be made by UK Labour's organisation sub-committee this month.

A one-time official in the Unison trade union, Murphy was named in a 2010 watchdog report that found a Unison brand that she was an official in had wrongly incurred expenditure on Labour-related activities. However, Murphy said she did not incur any of the expenditure herself.

A Labour Party spokesperson said: "It is for the members of Falkirk to select their candidate. The Labour Party will shortly be making a decision about whether the selection shall be an AWS.

"In the meantime, members' views about whether the seat should be declared an AWS are being considered. The final decision is for the national executive Committee, but the feelings of local members shall be considered as part of the process."