It follows a ruling at the Court of Session in Edinburgh that the elections would be incompatible with the European Convention on Human Rights.
The UK Government had set up a consultation process following a European Court ruling in 2005.
But legislation would not be introduced before Scotland's elections in May.
It is understood that a number of prisoners are already undertaking legal action to prevent the poll from taking place.
Three judges at Scotland's supreme civil court issued a declaration that the blanket ban on convicted prisoners voting was incompatible with their human rights.
A former prisoner, who was denied the right to vote in the last elections for the Holyrood parliament, took his case to the Registration Appeal Court in Edinburgh.
Lord Abernethy, who heard the appeal with Lord Nimmo Smith and Lord Emslie, said the May elections would take place in a way which was not compliant with the European Convention on Human Rights.
The judges said they had come to the view that they "should make a formal declaration of incompatibility to that effect".
The appeal arose after a serving prisoner, William Smith, had his application to be included on the electoral roll in 2003 rejected.
Lord Abernethy said Mr Smith's case was "of far-reaching importance".
"It is accepted by the government that there will be no amending legislation before the Scottish parliamentary election in May 2007," he said.
"We fully understand why the Government does not at this stage wish to rush forward with amending legislation but the fact remains that the Scottish parliamentary election in May 2007 will take place in a manner which is not Convention-compliant."
In 2005 a prisoner in England, John Hirst, who was serving life for manslaughter, won a decision over voting rights at the European Court of Human Rights.
source: BBC News Online (Scotland)