Richard Leonard has called for clarity on Labour's stance over the next steps of Brexit.
The Scottish Labour leader, in Brighton for the party conference, praised Jeremy Corbyn's leadership but said he would support the party taking a remain stance as Brexit talks rumble on.
Mark Drakeford, leader of Welsh Labour, also set out his stall on Sunday morning for a campaign to remain claiming up to 50,000 jobs could be lost in the country by a "crash-out Brexit".
Speaking on the BBC's Sunday Politics Scotland programme, Mr Leonard outlined the decision made by the Scottish executive from his own proposal to bring any deal decision back to the public.
He said: "The Scottish Labour party took a decision frankly in the wake of the European party election results that we needed to be much clearer, that we needed much greater clarity about the position that we were taking.
"For that reason the Scottish executive of the Labour party backed my proposal that we call for an affirmative vote that any deal should go back to the public; secondly, that on that vote there should be a remain option; and thirdly, that we would campaign unambiguously for remain.
"I would support the party taking that stance. I do think the time has come for clarity on this question and the Scottish Labour party, the Welsh Labour party take a similar view that we should be more overtly remain.
"But I think the key thing where we are in the chronology of Brexit is that Jeremy Corbyn's leadership has forced Boris Johnson into a position where he's got no mandate for his position of a no-deal Brexit and he's also embraced the idea and said categorically that Labour would put any deal back to the people."
Mr Leonard also threw his support behind ally Mr Corbyn, who earlier on Sunday vowed to serve a full term as prime minister if the party wins the next general election.
He added: "Jeremy Corbyn has been extremely strong in his leadership in getting the opposition parties to get together and block the Boris Johnson no-deal Brexit plan. We'll need to see whether Boris Johnson abides by that decision of parliament and that law.
"I think it gets into very interesting territory where there is a Prime Minister who in my view has got no mandate as prime minister for his government, who is standing on a policy which is in effect no-deal Brexit, for which there is no mandate either.
"The position is that we've said we want to put any deal back to the people and we've said in doing that we want a remain option to be on the ballot paper - but there would by the same token be a leave option on the ballot paper too.
"I guess the question is around what form that leave option would take and so there's been discussion about what the red lines of a Labour government negotiation with the EU would be."
Mandates came into question again when the MSP was also asked about another Scottish independence referendum.
Mr Leonard was previously been against the idea, but has come into line with Mr Corbyn's position that it would not completely be off the table after a few years of a Labour government.
He said: "The Labour position going into the general election whenever it comes will be that we oppose the creation of a separate Scottish state, that we oppose independence and therefore that we oppose the holding of a second independence referendum.
"Where there has been some discussion is around if there was to be a renewed mandate which showed not only electoral but demonstrable public support for the holding of a second referendum - then there would need to be some consideration given to that.
"We had an independence referendum just five years ago and that's got to be a factor in considering whether the circumstances are right for a second independence referendum to be held.
"All of the evidence shows that even people who voted yes in 2014, even some people who are supporting the SNP, do not think that the time is now for a second independence referendum.
"The circumstances under which the 2014 referendum were held were that the SNP had gained an overall majority - unprecedented, completely unexpected - and there was an understanding that there had never been an independence referendum and the time might be right to test it.
"What I'm saying is I don't see the circumstances today and I don't see them in the foreseeable future where we would be back in that kind of space again."