Barack Obama’s former ethics counsellor has accused the Trumps of using the White House “like the Kardashians used reality TV” to expand their business enterprises.

This week, Melania Trump refiled a $150m (£120m) lawsuit against the corporation that publishes the Daily Mail’s website for reporting rumours that she worked as a high-end escort in the 1990s. The filing argued that the article had hurt her chances of establishing “multimillion-dollar business relationships” during the years in which she would be “one of the most photographed women in the world”.

Ethics watchdogs are concerned that Melania Trump appears to be trying to profit from a high-profile position that is usually centred on public service.

Norman Eisen, Obama’s chief ethics counsellor, told Associated Press: “The Trumps are using the White House like the Kardashians used reality TV, to build and vastly expand their overall business enterprises.”

On Wednesday, Trump hit out at Nordstrom, the department store, for dropping his daughter Ivanka’s clothing and accessory line. “My daughter Ivanka has been treated so unfairly by @Nordstrom. She is a great person – always pushing me to do the right thing! Terrible!” the president tweeted.

His comments came after Nordstrom announced last week that it would stop carrying Ivanka’s label due to poor sales. “We’ve said all along we make buying decisions based on performance,” a statement issued at the time said. “We’ve got thousands of brands – more than 2,000 offered on the site alone. Reviewing their merit and making edits is part of the regular rhythm of our business.”

But the move followed a weeks-long boycott campaign organised by an anti-Trump activist group called “Grab Your Wallet”, who demanded Nordstrom sever its business ties with the Trump family. Three days prior to dropping Ivanka’s brand, Nordstrom also issued an internal statement in support of immigrants following the president’s executive order temporarily banning immigrants and refugees from seven Muslim-majority countries. It has maintained that the two were not connected.

After Trump’s tweet, the department store chain’s shares dropped but later bounced back. Trump’s tweets have in the past also affected shares in US automakers, Boeing and Carrier.

Asked about that tweet later, White House press secretary Sean Spicer said: “He has every right to stand up for his family and applaud their business activities, their success ... For someone to take out their concern with his policies on a family member of his is just – is not acceptable, and the president has every right as a father to stand up for them.”

An AP review of business filings has found that Melania Trump has not stepped away from companies that manage royalties from her name-branded products. As of Tuesday, she was listed in New York filings as the CEO of Melania Marks Accessories Member Corp, the holding company of Melania Marks Accessories LLC, both of which remain active. Those companies managed between $15,000 and $50,000 in royalties from her accessories lines, the Trumps’ May 2016 financial disclosure filing shows.

Scott Amey, general counsel of the Washington watchdog Project on Government Oversight, said the first lady’s ongoing enterprises are “another example of the first family blurring the line between public service and private business interests”.

Richard Painter, who advised former President George W Bush on ethics, said the Daily Mail lawsuit’s language suggests the first lady is engaging “in an unprecedented, clear breach of rules about using her government position for private gain”.

Melania Trump has maintained a relatively low profile since her husband’s inauguration and continues to live in New York, where her son Barron attends school.

The lawsuit was filed by her California attorney Charles Harder, who was hired in September to take on Mail Media Inc and Maryland blogger Webster Tarpley in the original suit.

The original suit, which was filed in Maryland, attacked rumours it described as “100% false” that Trump had worked for an escort service. Both Tarpley and the Daily Mail had issued retractions before the suit was filed.

The lawsuit against Tarpley was settled for “a substantial sum”.

Last week a judge dismissed the filing against the Mail, on the grounds that Mail Media Inc is not based in the state of Maryland.

The lawsuit submitted on Monday was filed in New York, where Mail Media Inc has offices. The updated filing said the article published in August caused Trump’s brand to lose significant value as well as major business opportunities that were otherwise available to her.

It stated: “[The] plaintiff had the unique, once-in-a-lifetime opportunity … to launch a broad-based commercial brand in multiple product categories, each of which could have garnered multimillion-dollar business relationships for a multi-year term during which plaintiff is one of the most photographed women in the world.”

Asked for comment about reporting of the lawsuit, Harder told the Guardian the filing was being “misinterpreted”. “The first lady has no intention of using her position for profit and will not do so. It is not a possibility. Any statements to the contrary are being misinterpreted,” he said.

The New York suit did not specifically refer to any plan to market products in Melania’s name during her tenure as first lady. It did state, however, that the Mail article “impugned her fitness to perform her duties as first lady of the United States” as well as “her duties in business”. It added that the article caused her “significant humiliation in the community and emotional distress”.

The lawsuit has raised further questions about the ethical implications of the Trump family’s business ventures.

In a break from past practice, Donald Trump continues to financially benefit from his global business empire. Previous presidents and their families have divested from business interests and placed their holdings in a blind trust, although there is no legal requirement to do so.

Trump handed daily management of the real estate, property management and licensing business to his adult sons and a longtime Trump Organisation employee.

Melania Trump’s marketing has also previously drawn scrutiny. In January, alongside a biography and list of her charitable work and interests, the new White House website took the unusual step of providing details of the Slovenian-born first lady’s magazine cover appearances and her jewellery line.

The website originally listed the brand names of Trump’s jewellery lines sold on QVC, but was shortly updated to remove any mention of QVC over concerns it could be seen as an endorsement.