David Cameron has been praised by a former member of Barack Obama’s cabinet for adopting an “innovative and effective” approach to business that has been critical in building Britain’s economic recovery.

In a boost to the Tories, who have faced accusations they have moved to the right with plans for a further £12bn of welfare cuts, Karen Mills, the former US cabinet member, endorses the prime minister’s handling of the economy.

Mills, who served in Obama’s cabinet as the head of the US small business administration until 2013, spoke up in favour of the Tories on the day the prime minister launched his party’s small business manifesto with an impassioned speech in the City.

In a Guardian article Mills writes: “David Cameron and the Conservatives have made small business and entrepreneurs a priority in ways that have worked – helping them to get credit, get their goods to new markets, reduce the burden of regulations and get access to government contracts. Their plans are making a difference. They are committed to continuing their focus, and that commitment to is critical to building economic growth and shared prosperity for UK citizens.”

The intervention by Mills came after a letter from 5,000 small business owners unravelled after it emerged that it contained dozens of duplicate names and one person who said they had never signed it. The letter, which was promoted by Tory small business ambassador Karren Brady, has been criticised after it emerged the document originated from Conservative party headquarters. This was discovered because the author of the document is listed in the metadata as “CCHQ-Admin”.

The Tories were delighted to win the support of Mills who met senior figures in Downing Street after leaving the Obama cabinet in 2013. She praised the Tories for reducing the burden of regulation on small business and for making it easier for them to compete for government contracts.

Mills writes: “When a storm hits, the smallest houses get hit the hardest. So it goes when a financial tornado reaches land. Large corporates weather the winds, but small firms often buckle. So it was during and after the financial crisis.”

In her article she makes no mention of the Labour party.