The Department of Health paid £1.5m to the financial advisers who acted for the government in the sale of the majority stake in Plasma Resources UK, the blood products company.

The most recent DH accounts reveal the sum was paid to French firm Lazard for facilitating the sale of 80 per cent of the firm to Bain Capital, the private equity firm founded by former US presidential candidate Mitt Romney.

Formerly DH-owned PRUK uses blood plasma to make treatments for haemophilia, immunological diseases and other conditions.

The sale was announced in July, with Bain paying £90m upfront, with an extra £110m due in 2018. The company has promised to invest £50m in PRUK and to maintain its headquarters in England.

Unison general secretary Dave Prentis said: “Not only has the government put profits ahead of patients yet again, but £1.5m of taxpayers’ money has been handed to the investment bank that was involved in the deal.”

A Department of Health spokeswoman said the company was used as a financial adviser to ensure “we got the best value for taxpayers”.

“Lazard’s fees were structured on a success basis, therefore they were only compensated if a buyer submitted a bid satisfactory to the Department of Health. Had a satisfactory bidder not been found, Lazard would not have been entitled to their fees,” she added.

The DH said Lazard advised them for the duration of the transaction, from June 2012 to August 2013.