A SENIOR French journalist has delivered a damning verdict on Boris Johnson, branding him a serial liar.

Marion van Renterghem, an award-winning reporter and author who has written a critically acclaimed biography on Angela Merkel, made the comments about the UK Prime Minister during a discussion about post-Brexit tensions.

She said the Tory leader had reached Donald Trump-levels of fibbing, and warned there will be no agreement between France and Britain while he and Macron remain in charge.

Speaking to TV station French 5 earlier this week, the reporter was asked about the current impasse between Paris and London over fishing rights and the migrant crisis.

"Johnson was made by Brexit, he made Brexit, he exists by Brexit and for Brexit,” von Renterghem explained. “It was thanks to Brexit that he became Prime Minister. He is ontologically Brexit."

She contrasted that to pro-EU Emmanuel Macron, whose political programme is built “against the very essence of Brexit”.

The journalist went on to cite filmmaker Peter Stefanovic’s viral video about Johnson.

She continued: “Boris Johnson, it's not just me saying it, is someone who lies all the time. Lying is for him, like Brexit, something ontological, essential, existential.

“There are people on Twitter, a lawyer by the name of Peter Stefanovic who made a video where he shows the repeated, factual lies Boris Johnson makes in the House of Commons every day. There is a whole book that lists them. It's on Donald Trump's level from that point of view.”

Speaking on the C politique show, von Renterghem added: “So he is someone who does not respect the treaties that he signs, it is someone who, after having made a declaration or having reached an agreement with the President of the [French] Republic, who will leak the exact opposite in the tabloids to agitate, and who is entirely focused on domestic policy issues.

“So Boris Johnson can't be talked to and it's not just Emmanuel Macron who says so. He is someone who has no word, no morals, and with whom it is extremely difficult to establish a link. I think that as long as these two men are in power, there will be no resolution to the Franco-British crisis.”

Tensions between Paris and London have peaked in recent days following yet another tragedy on the Channel, with 27 people dying last Wednesday after capsizing in a small dinghy.

France's interior minister Gerald Darmanin insisted Johnson must "take responsibility" for people attempting to cross the Channel, after the UK was excluded from talks over the weekend.

The Prime Minister was also accused of making a “mockery” of France after publishing a letter to Macron on Twitter. The document, which angered French leaders, set out steps to resolving the Channel crisis.

UK Government officials were subsequently uninvited to weekend negotiations with other European ministers about how to stop people from crossing the Channel.

Number 10 has been contacted for comment.

Translation by Assa Samaké-Roman