Under proposals yet to be approved by Holyrood, the SNP government wants to include a question asking respondents their "ethnic group" and whether they are Scottish, English, Welsh or British. Only one answer is allowed under the rules of the census to be held next year.
But a confidential government memo reveals that Labour, Liberal Democrat and Conservative MSPs are furious about the attempt to split up British and Scottish as options.
They want the government to adopt a version which combines all the options into a single ethnic group with only "Other" as a choice. They have made it clear that they will force a vote on the census – normally a non-partisan issue – and change its content if ministers do not drop their insistence on separating out identities.
They believe the SNP wanted the census question framed in this way to reinforce a sense of Scottish identity among respondents in support of its independence agenda.
One senior opposition member said: "The trouble is that Scottish is not a separate ethnicity so we will reject any solution that puts it that way. This is clearly an attempt by the Nationalists to hijack the census for their own narrow purposes, effectively politicising it."
The behind-the-scenes row has been revealed in a memorandum – obtained by Scotland on Sunday – written last week for senior ministers by enterprise minister Jim Mather, who is responsible for the census.
In the memo, Mather says Scotland's new official ethnicity classification, for Scottish official statistics and recommended for the 2011 census, was agreed by the Cabinet in May 2008.
A separate question on national "identity" would ask respondents whether they felt Scottish, English, Welsh or British.