Union members will not be "bounced" into picking sides in the independence referendum, the Labour leadership has been warned.

Many are still undecided and need to be given positive reasons to be able to consider their vote, Unite's Scottish secretary Pat Rafferty said at the Labour party conference in Inverness.

"We are being told by our members, many of whom are undecided, that they won't be bounced into taking sides in this referendum," he said.

"We'll continue to create as much scope and provide as much help as possible for our members to make an informed decision on the 18th of September 2014."

Choices should be made on the impact it will have on public services, a progressive tax system and welfare.

"We're a decent society where the vast majority of us contribute to the common good," he said.

"We want to know who will support our fight for our welfare system and the principle of universalism."

He was speaking during an opening session on the referendum campaign.

Labour, which has published its proposals for enhanced devolution, is campaigning for a No vote alongside Conservatives and Liberal Democrats in the Better Together group.

Dave Watson, of Unison, said his union has not picked a side yet.

"While I appreciate the referendum campaign has to have a formal Yes and No campaign, most of us in the labour movement have a huge difficulty with any campaign that includes the Tories," he said.

He called for a positive Labour vision of remaining part of the UK.

"Just rubbishing the SNP is not enough," he said.

Richard Leonard, of the GMB union, said the independence argument must be about shifting power to people, not from one parliament to another.

"Now more than ever, on the independence question, we need a distinctive Labour campaign," he said.

"I'm not talking about moving to the left or to the right, Old Labour or New Labour, for goodness let's just have a Labour party campaign.

"Let's get out of the slipstream of the nationalists and the unionists and be ourselves.

"It's no good simply saying what we are against, we need to tell people what we are for."

Scottish Labour deputy leader Anas Sarwar closed the debate by launching the party's 2014 "truth team", the first strand of its own referendum campaign.

The team will "reveal the facts" in the independence debate and "expose all the myths" of the SNP, he said.

The tactic is similar to one employed by the Obama presidential campaign team.

Mr Sarwar said: "We have a huge challenge on our hands and that is why we need to make sure that we run the most effective and biggest campaign we ever have done in any election in our history. We are going to make sure the Labour party is absolutely at the heart of that.

"Today we are launching one arm of the Scottish Labour referendum campaign, a campaign that recognises that the SNP so far have not had a good record in terms of giving Scotland the debate that it deserves with honesty and transparency.

"And that is why through this campaign we will make sure that we expose all the myths of the SNP campaign, reveal the facts and make sure we give the people of Scotland the debate they deserve."

Commenting on concerns about campaigning alongside Tories and Lib Dems, Mr Sarwar said: "We always recognised that Better Together has a job to do in terms of that cross-party non-party campaign."

He said the "truth team" will be followed by a "specific Labour case" for the Union launched before the summer.

"Let's be clear. Our vision for Scotland is not the same as the Tories or Lib Dems, or Ruth Davidson or Willie Rennie. What makes Labour different from the Nationalists is that they only have one cause: independence. For them, the limit of their ambition is September 18 2014," he told delegates.

"But unlike them, we don't and never will define our politics by allegiance to a flag. We define our politics by the values and principles of the labour movement.

"When we launch the Scottish Labour referendum campaign, we will do so with a compelling Labour case. A Labour case that has at its heart a vision that is a strong and confident Scotland, playing its full part in the United Kingdom."

Delegates also heard from Better Together leader and former Labour chancellor Alistair Darling.

He attacked SNP plans for a currency union in the event of independence.

"The Nationalists have been telling us that we can be part of a currency union and still follow a completely different economic policy from the rest of the UK. They say that we would be able to spend, tax and borrow what we want without any constraint," he said.

"Either they don't understand how currency unions work or, like they did with Europe, they are trying to deceive us again.

"The Nationalists want us to walk away and for the rest of the UK to create a eurozone-style sterling zone just so that Scotland can keep the pound."

Highlighting recent difficulties in Europe, he said: "You don't have to imagine what happens in a currency union. You only have to look at Europe to see exactly how it works. Germany is, in effect, telling the smaller countries what to do.

"No wonder there is a growing split in Nationalist ranks. A growing number of Nationalists realise that a currency union, whatever else it is, is not freedom."