A report published today by the Electoral Commission suggests both administrations should publish what their next steps would be should their sides triumph in the poll.
The 20 December deadline was suggested by the commission in an attempt to provide some clarity about what would happen in the immediate aftermath of either a Yes or No vote. The UK Government has ruled out pre-negotiating an independence deal before the 18 September poll.
The commission, however, believes there should be more information on how the terms of independence would be arrived at, so that voters understand how competing claims made by campaigners will be resolved.
The report added: “We believe this is important for voters. We therefore recommended the Scottish and UK Governments clarify what process would follow the referendum in sufficient detail so as to inform people what would happen if most voters voted Yes or if most voters voted No.”
A joint statement should be agreed by 20 December to coincide with the expected Royal Assent to the Referendum Bill, the commission suggested.
Last night, both governments said they were working together to produce a joint statement on events after the referendum, which takes into account the implications of a vote either way. The statement is likely to reflect the SNP’s transition plan to negotiate such issues as the size of national debt an independent Scotland would inherit and the currency arrangements in the event of a Yes vote.
The statement is also likely to take into account any plans that the Unionist parties come up with to strengthen devolution in the event of a No vote.
A Scottish Government spokesman said: “We are continuing our discussions with the UK government.”
A Scotland Office spokesman said: “The two sets of civil servants are working well to provide the type of material requested by the Electoral Commission.
“This should not be confused with negotiations. As ministers have said on many occasions, there will be no pre-referendum negotiations.”
The report also said the Scottish independence referendum is on track to be a well-run poll.
The authority looked at preparations one year before people in Scotland are asked whether they want to end political union with the rest of the UK. John McCormick, Electoral Commissioner for Scotland, said: “On 18 September next year, voters will be asked to decide the future of Scotland and they need to have confidence in the result.
“There must be no doubt that the referendum was fair and transparent and there were no barriers to voters or campaigners taking part.
“The rules and the plans for delivering the poll across Scotland underpin the whole referendum and we are encouraged by the progress we have found.”
The commission published its interim report just days after the Scottish Parliament endorsed the general principles of the Referendum Bill.
The legislation lays the groundwork for the poll and sets the franchise, which will see the lowering of the voting age limit to 16 years old.
The Transparency of Lobbying, Non-party Campaigning and Trade Union Administration Bill will change campaign spending rules for non-party campaigners in the year before a general election.