Justice Secretary Kenny MacAskill came under fire yesterday after sending a tweet that appeared to compare Aberdeenshire Council with attempts to disenfranchise black voters in the southern states of America in the 1890s.

On Thursday, Alex Salmond announced a ban on councils pursuing £425m in poll tax arrears using electoral rolls enlarged by the wave of voter registration in the referendum.

The move was prompted by Aberdeenshire and Labour-led Aberdeen City Council saying they hoped to find tax-dodgers using the new rolls.

On Friday night, the Justice Secretary tweeted: "In southern states of USA post-civil war poll tax and other ruses were used to disenfranchise Black people. In 2014, we have Aberdeenshire."

In the 1890s, every southern US state changed its constitution to make it harder for black people to vote, using poll taxes, literacy tests and other disenfranchisement schemes.

Opposition parties said MacAskill had trivialised the suffering of millions with the comparison.

Labour justice spokesman Graeme Pearson MSP said: "If Kenny MacAskill spent less time sending inappropriate tweets and more time being a competent Justice Secretary then maybe we wouldn't be seeing him stumble from crisis to crisis."

Later in the day, the SNP denied MacAskill was making a comparison between the two situations and criticised other parties for ''standing shoulder to shoulder with the Tories'' on the issue of recovering debt.

Tory MSP Murdo Fraser became embroiled in the row when he went on Twitter to mock the nationalist denial.

Fraser mimicked MacAskill's earlier tweet following the announcement that Jean-Claude "Baby Doc" Duvalier, the brutal former Haitian dictator whose regime was accused of committing crimes against humanity, had died of a heart attack.

Fraser tweeted: "Baby Doc Duvalier has died. Unlike Alex Salmond, who is alive. No comparison between the two."

He then tweeted a link to a news story about the MacAskill controversy, which included the SNP denial. Fraser added: "Interesting line on 'comparisons' from the SNP press office."

SNP MP Pete Wishart then entered the fray, advising Fraser to delete the tweet, and said it was a "seriously stupid thing to say". Fraser replied: "Genuinely sorry if you cannot detect an ironic reference to Kenny's tweet."