Opinion polls indicate the daughter of Jean-Marie Le Pen, a convicted racist and former National Front president, will be Mr Macron’s main challenger in the planned election next year.
On Saturday, the French finance minister said: “The election of Marine Le Pen, we all know that is a possibility.”
Mr Le Maire told BFM television: “It is a political possibility and it must be opposed.”
Speculation has mounted that Ms Le Pen could win the next presidential election by capitalising on the coronavirus pandemic and its economic impact.
Mr Macron’s handling of Covid-19 has divided opinion, with some people saying he has done better than other European leaders, while others in France accuse his administration of incompetence.
The country has recorded more than 81,000 deaths and around 3.4 million infections since the start of the pandemic, and faced criticism for the slow rollout of its vaccination programme.
Ms Le Pen, who is Mr Macron’s likely challenger in the 2022 election, heads the far-right National Rally party, previously known as the National Front.
In 2016, she called Donald Trump’s election as US president “an additional stone in the building of a new world”.
Additional reporting by agencies