The reelection campaign of French President Emmanuel Macron has been met with quite the obstacle as he prepares to hold his first big rally on Saturday over his affiliation with the US consulting company, McKinsey and Co.

"The McKinsey Affair" was named after a US firm hired to advise Paris on its COVID-19 vaccination campaign and other policies.

A report from the French Senate questioned the government's usage of private consultants and accused the American firm of tax dodging. Macron's rivals are using this to undermine his bid at reelection, and it is following him to his campaign stops just days before the April 10 vote, the first round of the elections.

Macron's supporters are hoping that he can overcome this obstacle during his rally in Paris as the centrist pulls ahead in the polls against his further right opponents such as Marine Le Pen and Eric Zemmour.

Critics are describing the government's step of spending some 1 billion euros on a US consulting firm as some sort of "privatization" and "Americanization" of French politics, calling on the Elysee Palace to be more transparent.

The French senate controlled by Macron's opposition had published a report last month on the use of private consulting firms, and it found that Paris' spending on such contracts had increased two-fold over the past three years, despite questionable results. The Senate also put the issue of conflict of interest on the table.

The report said McKinsey had not paid corporate profit taxes in France for over a decade, opting for a system of "tax optimization" through its parent company in the state of Delaware.

McKinsey defended its work in France and issued a statement saying it "respects French tax rules that apply to it."

McKinsey advised the French government on its COVID vaccination campaign, which did not have the greatest start but later gained ground and became of the world's most comprehensive. Macron had also used outside consultants on housing reform and asylum policy, among other measures.

The Conservative majority Senate found that spending on outside consulting was higher under former President Nicolas Sarkozy than under the current administration and that such firms made even less in France than in the UK or Germany.

Budget Minister Olivier Dussopt claimed that state spending on consultants was about 0.3% of what Paris had spent on public servants' salaries last year, accusing campaign rivals of inflating the amount it made in a bid to boost their own ratings.

Macron's rivals say the McKinsey affair gave life back to concerns that Macron and his government were beholden to private interests and out of touch with the concerns of ordinary voters.

Today, Macron is haunted by questions about the affair wherever he goes, and he is arguing that the campaign "should be about purchasing power, how to settle security problems, how to end the war [in Ukraine]," telling voters not to "make it about a false issue."

A woman who had lost her father to COVID-19 filed a lawsuit against the US firm, accusing it, alongside other consulting companies, of missing public funds when Paris hired them for advice on masks and vaccine supplies.

She and others have filed cases involving the government’s handling of the pandemic, making several accusations against the Elysee Palace.