Sir John Curtice added that the demand for a second referendum in some quarters of the party could dominate the discourse at the event in Edinburgh next week at a time when the party is still refining its fiscal message to the electorate.
A poll by Progress Scotland last month found that keeping the pound as the national currency for the long-term in an independent Scotland had the support of 47 per cent of the 2,000-plus respondents, while switching to a Scottish currency in the short-term was only favoured by six per cent.
A joint motion will be submitted at the conference to make a new Scots currency official party policy after independence once tests are met – instead of retaining the pound as part of a currency union with the UK.
“Until they sort out what their policy is, they can’t begin to sell it,” said Curtice.
“An obvious reason for delaying [the timing of another referendum] is they are supposed to be sorting out their fiscal policy.
“They will then have to start presenting their case to the public. It seems to me that sorting out fiscal policy is a crucial stepping stone to being able to hold a referendum.
“Selling the idea of a separate currency will be substantial work.”
Nicola Sturgeon is expected to make an announcement on whether the Scottish Government will push for a second independence vote at the party gathering.
Several prominent members of the former Yes campaign believe the ongoing Brexit row at Westminster means a vote should be organised sooner rather than later.
But Curtice pointed to the most recent polling, which suggested there was no sign that support for independence had increased.
He added that the uncertainty over the UK’s future political direction also made the case for independence more difficult.
“Until we know what is happening with Brexit, it is hard to make the argument on whether Scotland will be better off in or out of the EU,” he said.