THE chairman of the Scottish Labour Party has been drawn into the Falkirk vote rigging scandal after it emerged he was directly involved in the campaign to sign up union members to influence the constituency selection battle.

Emails reveal party chairman Jackson Cullinane was in contact with leaders of the Unite union as it tried to secure the selection of its preferred prospective parliamentary candidate .

The latest development increases the pressure on Scottish party leader Johann Lamont to take action over the crisis which has dogged the party for months.

The Unite union has been accused of trying to pack the Falkirk Labour Party with its supporters to ensure its preferred candidate won a local selection. People were even signed up as party members without their knowledge.

Neither Opposition leader Ed Miliband nor Ms Lamont has ordered an inquiry into what went on, although other Labour heavyweights including Alistair Darling have said questions need to be answered.

The emails that have now emerged show on October 23 last year Mr Cullinane, who is the union's political officer in Scotland, wrote to Tom Warnett, political co-ordinator at Unite in London. Mr Cullinane was seeking clarification about aspects of the Labour Party sign-up campaign among union members.

The email was copied to the head of the union in Scotland, Pat Rafferty.

The exchange makes it clear that the sign-ups were specifically designed to influence the selection of the union's favoured candidate in Falkirk, Karie Murphy.

Mr Cullinane referred to "Karrie's note", presumably a reference to Ms Murphy, asking whether a tear-off slip would be included on union correspondence inviting Labour Party membership. Instead, a separate form to that effect was included.

Mr Cullinane added: "As you get the forms etc in, will a communication then go out from your end to the relevant branch secretaries to have the new members registered as CLP (Constituency Labour Party) delegates and affiliations then paid from the political fund centrally?"

Mr Warnett confirmed regarding the payment that his boss, political director Steve Hart, "will be okay with it as other regions already do. The money will come from the regional political budget which is administered centrally (ie. by me)."

He said: "I sort out a cheque down here and send it all off to Labour," adding: "Of course, joining a member by cheque, and one they haven't even written themselves, will mean a lot of drop-off after the first year, so it's not ideal in the long term but should be okay for the selection."

Pressure continued to build at the weekend for Mr Miliband to re-open the party's inquiry into Falkirk and publish its initial report into the affair.

Media scrutiny has also turned to the election of Len McCluskey as general secretary of Unite amid claims that lapsed or even dead members of the union voted in that contest.

A Scottish Labour spokesman said: "Members in Falkirk will have the opportunity to select a candidate on December 8. The police are considering the content of emails and once their work has concluded, the Labour Party will consider what, if any, further steps are needed to be taken."

SNP MSP Annabelle Ewing said: "This is a damning revelation, and means Johann Lamont can no longer get away with saying nothing of substance on the issue.

"Despite the fact she is supposed to be leader of the whole Labour Party in Scotland, Ms Lamont has stood by and watched her party implode in Falkirk without doing anything.

"Given this new evidence, she can no longer leave this matter to her party bosses in London."