In a damning letter which exposes the rift in the party around its Brexit position, Kezia Dugdale said she had been “shocked” to learn that Mr Leonard had intervened in a pro-EU statement written by Labour MEPs Catherine Stihler and David Martin for the programme of the Scottish Labour conference, which opens tomorrow.
She added that Mr Leonard had insulted the pair by failing to ensure their years of service were marked at the conference.
Her letter also criticised his stance on Brexit and expressed “disappointment” at his recent remarks that he would rather there was a Labour leave deal than a second referendum to remain in the EU. However, a Scottish Labour source said that there had been a “genuine misunderstanding” and Mr Leonard has written to both MEPs to apologise.
In her letter, Ms Dugdale claims that, on the instruction of Mr Leonard, and without the MEPs’ consent, a description of Brexit being “a tragedy for our country” and their support for a second referendum was deleted.
She wrote: “I wish to formally complain about the way in which Catherine Stihler and David Martin have been treated ahead of conference. From what I can see from the agenda, there is no formal opportunity for them to speak or indeed a formal item to thank them for their combined 55 years of electoral service to the party.
“If that wasn’t bad enough, I was shocked to discover from Catherine that her statement in the conference guide had been amended without her consent. When that was challenged, she was told it was on your direction and that you had the final say on what was printed.”
The letter repeats the deleted section which states: “Brexit is a tragedy for our country and for the workers and communities that Labour represents. That’s why David and Catherine fully support a people’s vote with the option to remain in the EU.”
This section was replaced with: “The complete mess the Tories have made of Brexit means they are putting Scottish people’s jobs and our industries at risk. Labour will always put them first.”
Ms Dugdale added: “I find that wholly inappropriate and I can’t possibly understand why you would seek to censor her final words to party members, especially since what she states is party policy and has been since last September.
“Can I encourage you to please take urgent steps to rectify what I consider to be a considerable insult and ensure that we thank these two outstanding MEPs properly at conference.”
The letter also spells out Ms Dugdale’s concerns about Mr Leonard’s views on Brexit. She states that she has found the party’s stance “disappointing” and that it was “in this context” that she was making her complaint.
Last week Mr Leonard said he would rather have a Labour Brexit deal than a second EU referendum – but that he would still back Remain if a second vote was held.
He has faced criticism for failing to back a second referendum despite Scotland voting to Remain in the 2016 vote.
Ms Dugdale resigned as party leader in August 2017 citing her differences with UK leader Jeremy Corbyn over Brexit as one reason to quit. At last year’s Scottish Labour conference, she was instrumental in launching the campaign group Scottish Labour for the Single Market.
She wrote: “You know that I’ve found the party’s position on Brexit and a second EU referendum disappointing for some time. As I said at group last week and repeatedly over the past few months. I don’t believe there is such a thing as a good Brexit or indeed a ‘jobs first Brexit’.
“I remain utterly convinced, rooted in all the evidence I have seen, that it will be immensely damaging for the Scottish and UK economy. A price which will once again be paid by those in low-paid and insecure work, the very people we seek to represent.
“The move towards supporting a People’s vote is a welcome one, but it should have happened much much earlier. I note... that you’d sooner we left the EU than give people a final say.
“That’s disappointing for the many party members who fervently back a final say and indeed all of our voters who are now a bit lost for a home.”
It is believed that the letter was shared with all Scottish Labour MSPs in Holyrood and the seven MPs in Westminster. A source close to Ms Dugdale said she had received support from MSPs for her letter. “Kezia felt it was important that all elected members should know that their words can be changed and printed without their permission. She has received a lot of supportive responses from MSPs who also believe that Catherine and David are being treated very shabbily by a party they have worked so hard for, over so many years.”
A spokesperson for Ms Stihler said: “Catherine is a long-standing supporter of a People’s Vote and will be making her views clear as a Labour Party member at this weekend’s conference.”
Party sources claimed there had been a failure of communication between Mr Leonard’s office, Ms Stihler and party general secretary Brian Roy which led to the changed paragraph remaining in the conference programme rather than it reverting to the original words.
A Scottish Labour source said: “This was a genuine misunderstanding and Richard has written to Catherine and David to apologise.”