The SNP has been urged to sack a council candidate in Glasgow after a picture emerged of him on a march honouring a former IRA member.

Allan Casey is shown hitting a drum at an event remembering Martin ‘Doco’ Docherty, who was a volunteer in the terror group until he was shot dead in 1994.

A spokesman for the Scottish Tories said: "It's inexplicable for the SNP to allow someone like this in its ranks. He should be dropped immediately, there's no other way for this to go.”

Since 2015, Casey has been working as a parliamentary assistant in the office of the SNP MSP for Glasgow Provan, Ivan McKee.

However, the Sunday Herald revealed that Casey had posted a series of hardline messages on Facebook in support of the IRA before he joined the SNP.

In 2012, he flagged up the “Annual Volunteer Martin Doherty Commemoration Weekend Events” and in the same month wrote: “Volunteer martin Doherty rfb no1 real pride of govan, up the provos – sinn fein abu [sic].”

Casey also asked for help in raising the organisation’s social media profile and reminded people of “band practice” for the pro-Doherty group.

Picture: Casey

In 2012, he also paid paid tribute to IRA volunteers Declan Martin and Henry Hogan: “Killed on active service 28 years ago today while engaging in a gun battle with undercover SAS scum.”

In the same year, he wrote: “Your deeds would shame all the devils in hell – f**k the brits, remember bloody Sunday 30th January 1972.”

Doherty had been in the IRA until he was killed by the UVF, a loyalist terror group.

According to the SNP, Casey received a warning about his behaviour, but he subsequently passed vetting to be an SNP council candidate in May.

He has since been nominated by an SNP branch and is expected to contest the election.

A senior SNP source confirmed that Casey is the man in the picture hitting a drum. The event is believed to have taken place seven years ago.

The row follows an earlier controversy where SNP MSP John Mason claimed that the members of the IRA who killed three Scottish soldiers could be considered as “freedom fighters”.

After being asked on Twitter whether he would support a private prosecution of those suspected of murdering the three men, Mason replied: “You say Irish murderers. Others say freedom fighters. I support Scottish soldiers if they do good but not if they do bad.”

First Minister Nicola Sturgeon apologised to the families of the dead soldiers for the “upset caused” by Mason’s comments. The MSP also said sorry.

An SNP spokesperson said: "This has already been reported and dates from several years before Allan was a member of the SNP."