AN SNP MP has written to the Electoral Commission over concerns that groups spending thousands on pro-Union ads flouted online advert rules in the run-up to last week's election.

It was revealed earlier this week that in the days before the Scottish Parliament election third-party campaigns - with no clear details of where their funding comes from - spent tens of thousands of pounds on digital ads pushing Scots to vote tactically.

Brendan O'Hara called on the Electoral Commission, the independent election regulator, for a "comprehensive response", saying that the ads “may be contrary to election law and regulations”.

An openDemocracy report highlighted groups that had pushed money into social media adverts with a lack of transparency of where the funds came from.

The site found a group called Young Unionists spent more than £20,000 on Facebook ads, including more than £5000 in the final days of the campaign. Tens of thousands of voters were pushed to the VoteUnion tactical voting tool.

Under new election legislation, digital adverts in Scotland are supposed to carry details of who paid for them. But Young Unionists' ads had no disclaimer and there was no name attached to the campaign.

READ MORE: Did Unionist tactical voting ads stop SNP from winning key target seats?

Young Unionists did register as a non-party campaigner in the Scottish election with its secretary listed as Maximillian Young who was involved in a campaign called Capitalist Worker, which spent £65,000 on anti-Jeremy Corbyn ads in the 2019 General Election without declaring any donors.

Another Facebook page, Vote Union, last week spent £3012 promoting its tactical vote calculator “to stop an SNP majority”. 

The pro-Trump student group Turning Point UK spent £3700 on Facebook ads last week, all focused on the Scottish election. Between Tuesday and Thursday, at least 70,000 voters saw a Turning Point ad that said “vote ConservativeLabour or Liberal to remake Scotland!”.

The Turning Point UK ads had no imprint so it was unclear who paid for them but they were all targeted at people in England, perhaps in an attempt to evade Scottish legislation on digital political ads.

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Writing to the Electoral Commission, O’Hara (above) said: “I would be very grateful for a comprehensive response to these concerns at the earliest opportunity.

“It is vital the electorate has full confidence in the electoral process and that open democracy and accountability can be demonstrated.”

O'Hara previously sat on Westminster's Digital, Culture, Media and Sport Committee and has called on the Electoral Commission to publish evidence surrounding secretive donations in the Brexit referendum.

The Electoral Commission did not confirm whether an investigation would be launched into the ads in last week's Holyrood election, but a spokesperson did say the commission had "received a letter from Mr O’Hara and will respond in due course".