THE SNP's "Tory-free" Scotland slogan was likely a tactic to "galvanise" grassroots members, rather than something to be used among the wider public, a political communications expert has said.

The party faced a backlash internally and from opposition parties after Humza Yousaf used the phrase several times when addressing activists at a National Council event in Perth.

Pete Wishart, the party’s longest-serving MP, said he would not be using the phrase in his campaigning, while the Aberdeen Independence Movement branded it “counterproductive”, pointing out that the SNP would need Tory voters on side to achieve independence.

But Jennifer Lees-Marshment, a professor in political marketing and management at the University of Dundee, has suggested the SNP may not go on to use the slogan widely in campaigning and may have been playing to an internal party audience.

She told The National: “The message was put to an internal audience, you’ve got to bear that in mind. They may be more receptive to it than those who aren’t SNP voters.

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“It could just be internal language to galvanise the grassroots at a time when they’re beginning to worry the SNP stronghold and share in the polling [is slipping].

“It could be nothing and hopefully they will come up with something more positive that is about the people of Scotland, that is about the voters, more than their opposition.

“They [the SNP] are speaking to people’s surface level emotions in going for an anti-Tory position and the idea that if you get rid of the Tories, you’re protecting Scotland’s sovereignty and freedom, so that’s possibly where it’s coming from.”

Lees-Marshment added, however, that the SNP should consider coming up with a less negative phrase that appeals more widely to voters on the fence they could be targeting. 

She added: “Political marketing research has shown that although negative communication gets attention, it won’t necessarily get positive support.

“It’s a highly emotive and quite single-minded [the slogan]. It’s attacking an opposition party, it’s not talking about voters in Scotland, it’s not talking about what policies the SNP are going to put forward.

“Ahead of a UK General Election, you should be focusing on the voters. The SNP has a prime opportunity to win over Conservative voters who don’t want to give their vote to the Conservatives anymore but also don’t want to give it to Labour.”

The slogan has been criticised by some who argue it has potential connotations of wiping out conservative values from Scotland, or may suggest Tory voters should be ignored.

Scottish Tory leader Douglas Ross has claimed Yousaf’s Tory-free rhetoric is a sign of treating Conservative voters with open contempt.

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He described the comments as “insulting” and said the SNP “should suffer at the ballot box” for the “divisive” language.

But Toni Giugliano, SNP General Election candidate for Falkirk, said politicians should not be underestimating the intelligence of voters who he believes understand the SNP is talking about getting rid of Tory MPs, not voters.

He said: “Let’s treat voters with some respect here, they know exactly what they’re doing and they know very well the way to get rid of this Tory government is to unseat Tory MPs.

“That’s what this message talks about, it’s not talking about Conservative supporters or voters.

“Politicians should stop underestimating voters. I think over the years we’ve seen more voters voting tactically for example, particularly post-2014 referendum.

“Why is it okay for the Tories to use attack lines to get the SNP out and stop the SNP but when we use the same attack line then it’s suddenly inappropriate?

“The electorate are switched on and they know [what we’re talking about].”