New figures from the Electoral Commission show the party spent £99,000 on the Holyrood by-election in August, compared to £90,000 on the referendum on leaving the European Union in 2016.

The SNP’s Shetland candidate came second to Lib Dem Beatrice Wishart in the poll.

Hopes fade that Brexit breakthrough will come in time for summit

The SNP have defended themselves as the 'strongest advocate' for Scotland. Picture: File

The Scottish Liberal Democrats have hit out at the SNP over the election spending figures, which show the party spent 12.8% of the total allowed on the Brexit poll.

But an SNP MSP dismissed the attack as “incoherent and frankly laughable”.

Lib Dem Orkney and Shetland MP Alistair Carmichael claimed the party’s spending on the EU referendum is evidence of the “cynicism of the SNP leadership’s position on the EU”.

He said: “The fact that the SNP spent more on the by-election in Shetland than in the entire EU referendum campaign speaks volumes. It is disappointing but hardly surprising, considering how much lucre they flashed around in the Northern Isles over the summer.

The SNP had hoped to cause an upset by beating the Liberal Democrats in the Shetland by-election. PRESS ASSOCIATION Photo.

“Apparently one more vote for independence in Holyrood was worth more to the nationalists than their European values. It’s a shame they don’t put their money where their mouth is.

“It shows the cynicism of the SNP leadership’s position on the EU. They tell their supporters one story on Europe, but their actions tell another.

“They back the EU with words, but the truth is that they see Brexit as a golden opportunity to push independence at the price of our country’s well-being.”

The Shetland by-election, which was called after the resignation of Tavish Scott, saw Ms Wishart take the seat with almost 48% of the vote.

The First Minister, along with a number of other high-profile SNP members, made several visits to Shetland ahead of polling day.

SNP MSP Rona Mackay said: “This is an incoherent and frankly laughable attack from the Lib Dems.

“The SNP has been and remains the strongest advocate for Scotland’s place in Europe - and, of course, in the Brexit referendum Scotland voted overwhelmingly to Remain.

“The reality is the Lib Dems would rather see Scotland taken out of the EU with a Tory Brexit than be a member state of Europe in our own right.

“They should be helping to remove Boris Johnson from office so that we can hold a general election and stop Brexit - instead of pandering to Tory voters as (Lib Dem leader) Jo Swinson has been doing.”

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SNP spent more on Shetland by-election battle than Brexit referendum