Malcolm Scott, who according to a judge had gone missing earlier this year, appeared at the Tories' summer party in London along with the Prime Minister and his Cabinet.
Labour MP Graeme Morrice said the revelation was a disgrace. Scott was until recently one of the party's biggest donors north of the Border, pouring in more than £1.6 million in corporate and personal contributions.
He was close to Foreign Secretary William Hague, allowed David Cameron use of his private jet, and even hired singer Bryan Ferry to play at his birthday party.
However, the grain and property tycoon's empire was put into administration last year after his companies failed to repay millions of pounds in banks loans. Scott was then sequestrated, the Scots term for bankruptcy.
His mother, father and wife were also made bankrupt after the collapse.
One of Scott's creditors, Courseworks Ltd, also went to court over nearly £740,000 in unpaid gardening and landscaping work on Scott's former mansion in Kirknewton.
Administrators working on Scott's case have also been trying to trace assets such as £215,000 of Jordanian artefacts and Persian rugs worth nearly £45,000
Mr Morrice, the MP for Livingston, said: "It is a slap in the face for the individuals and businesses still waiting for their money to see Scott at such a glitzy event."
A Tory spokesman did not respond to a request for comment.
Mr Scott could not be contacted.