THE trade union Unite has been accused of "absolutely desperate" behaviour after it instructed its members how to vote in the Scottish Labour leadership contest.

Unite included a "mock" ballot in a mail shot along with the real voting slip, next to the edict: "Fill out the enclosed ballot paper like the example below." The dummy ballot supported Unite's two favoured candidates - left-wing MSP Neil Findlay and MP Katy Clark.

The leadership contest, triggered by the bitter resignation of Johann Lamont, is between Findlay, Sarah Boyack MSP and MP Jim Murphy.

The deputy poll is a two-way battle between Clark and Lothians MSP Kezia Dugdale.

Unlike future UK leadership elections, which will be conducted using one-member-one-vote, the Scottish contest is being fought under the party's old electoral college.

This system gives an equal one-third vote share to trades unions and socialist societies, parliamentarians and party members.

Trades union affiliates are responsible for sending out ballots to their members.

The GMB also included pro-Findlay literature in the ballot packs received by its members.

It read: "GMB Scotland had a thorough process where we invited all candidates to be interviewed. After speaking to all contenders, we are recommending Neil and Katy."

At the right-hand side of the endorsement was a ballot-style montage, which shows Findlay and Clark receiving the seal of approval in the form of a "1".

A senior party source said: "This mock ballot is absolutely desperate stuff from Unite. I don't know if it's arrogance or incompetence, but it's about time the union's leadership behaved in a responsible way with the party."

Unite is helping fund ­Findlay's campaign and its general secretary, Len McCluskey, has been scathing about Murphy. The union was last year caught up in a major row over its attempt to influence a Labour selection contest in Falkirk.

Meanwhile, Findlay and Clark have also been unhappy at the ballot packs sent to ordinary members by party headquarters.

Scottish Labour's procedures committee agreed that a booklet containing endorsements from parliamentarians should be included, but not testimonials from affiliates or local constituency parties.

MPs, MSPs and MEPs ­overwhelmingly support Murphy, and Findlay's camp believe the booklet created the impression of him having more support than the other candidates.

Eight unions, all of which have declared for Findlay, have made a formal complaint to the party about the issue.

Senior party figures believe the mock ballot and the booklet row confirm the need for future Scottish leadership contests to be fought under one-member-one-vote. At a hustings on Thursday night, Murphy and Boyack backed a move away from the college, but Findlay did not.

Under the college rules, non-Labour members and supporters can get a vote via their union, a practice dubbed no-member-one-vote.

In addition, the vote of one parliamentarian has the same weight as that of 168 party members. It is also possible for ­individuals to have multiple votes. An MP who is a member of one trade union and a socialist society, as well as being a party member, would have four.

Pat Rafferty, leader of Unite Scotland, said: "Unite members will cast their vote in the privacy of their own home. It is ridiculous and insulting to our members to suggest that campaign information from the union does not support them in their decision-making."