Angela Merkel, who in her new memoir raises fears for the western democratic order with Donald Trump as US president, has also expressed deep concerns about the outsized role to be played in Trump’s administration by Elon Musk.

The former German chancellor, who during Trump’s first term was given by some observers the designation of “leader of the free world” usually reserved for US presidents, said 16 years in power had taught her that business and political interests must be kept in fine balance.

Asked by Der Spiegel magazine in an interview whether the challenge posed by Trump had grown since he was first elected in 2016, Merkel responded: “There is now a visible alliance between him with the big companies from Silicon Valley which have enormous power through capital.”

Musk, who is advising Trump on his second term, has been tasked by the president-elect with leading a newly created department of government efficiency along with Vivek Ramaswamy. Merkel said the SpaceX and Tesla chief’s financial entanglements made such an appointment highly problematic.

“If a person like him is the owner of 60% of all satellites orbiting in space, then that must be a huge concern for us along with the political issues,” she said. “Politics must determine the social balance between the powerful and ordinary citizens.”

She noted that in the 2007-08 financial crisis during her first term as German chancellor, “the political sphere was the final authority that could straighten things out” with measures such as bailouts coupled with new regulations.

“And if this final authority is too strongly influenced by companies, whether through capital power or technological capabilities, then this is an unprecedented challenge for us all,” said Merkel, whose 700-plus-page tome will be released on Tuesday.

She said one of the benchmarks setting free societies apart was clear checks on corporate power and the sway of the ultra-rich. “In a democracy, politics is never powerless against companies,” she said.

Of social media platforms such as Musk’s X, Merkel said: “It is important to counterbalance the furore in social media, such as that stirred up by the AfD in this country,” referring to the far-right Alternative für Deutschland party, which is now placing second in opinion polls before a 23 February snap election.

Merkel acknowledged that she had supported Hillary Clinton and Kamala Harris in their ultimately unsuccessful presidential bids against Trump and said their defeats had filled her with sadness.

In extracts from the memoir published in the German weekly Die Zeit, she says Trump as president approached relations with longstanding allies as aggressively transactional, “like the real estate developer he was before he entered politics”.

She found him to be particularly fascinated by the Russian president, Vladimir Putin, and “politicians with autocratic and dictatorial traits”. Merkel has faced strong criticism since leaving office that she failed to establish clear red lines with Putin and made Germany far too reliant on Russian gas.

Musk, the world’s richest man, campaigned hard for Trump and is helping manage his transition back to the White House, including weighing in on appointments, sitting in on telephone calls with world leaders such as Ukraine’s Volodymyr Zelenskyy and discussing cutting a third of the $6.75tn federal budget.

Musk’s corporate holdings have reportedly received $15bn in public contracts, a figure expected to rise during Trump’s tenure.