Mr Blackford, the MP for Ross, Skye and Lochaber has faced calls to resign as Chairman of the Golden Charter Trust, a funeral plan provider that has benefited from companies that are believed to have sold arms to Saudi Arabia.
The SNP has been among the chief critics of the UK’s role in selling arms to Saudi Arabia, which has faced international condemnation for bombing Yemen.
Golden Charter Trust, which pays Mr Blackford £3,100 a month for eight hours work per quarter, has a large collective investment in Artisan Global Equity fund, which makes money from investing in defence companies including Harris Corporation and Raytheon.
Labour’s Shadow Scottish Secretary Lesley Laird said: “Ian Blackford should either divest from these companies, or better still, resign his chairmanship of Golden Charter, and provide his constituents in Ross, Skye and Lochaber with a full-time MP,”
The career of Mr Blackford and his business interests have previously caused controversy.
He was mocked in the House of Commons for claims of being ‘a simple crofter’ despite a long career as an investment banker in the City of London.
Tory MP Greg Hands said at the time: ““I noticed him describing himself as a ‘simple crofter’. I have a little bit of doubt about this.
“I had a career in the City and I don’t recall him being a simple crofter at that time.
“Maybe that was his codename on his Bloomberg terminal as he was buying and selling financial assets.”
Mr Blackford, who has regularly pressed the Prime Minister to halt arms sales to Saudi Arabia, told the BBC’s Sunday Politics: “Is anybody really saying that people shouldn’t invest in British Aerospace, which is a company that makes equipment for the UK defence industry? That is just nonsense.
“The SNP is very clear that the government should take action to make sure that we are not selling arms to Saudi Arabia. That is for humanitarian reasons, and is a very different proposition altogether.”
Andrew Smith of the Campaign Against Arms Trade, told the Mail on Sunday: “Ian Blackford has been among the most vocal opponents of the UK’s role in the war. We urge him to do everything he can to ensure his personal business is consistent with his political positions. By investing in the arms industry, Golden Charter Trust Limited is supporting it.”