Mathieu Bastareaud (File)

Paris - French Prime Minister Francois Fillon has written to his New Zealand counterpart John Key to aplogise for the "unacceptable behaviour" of France centre Mathieu Bastareaud.

The 20-year-old Stade Francais player is at the heart of a furious row after lying over an alleged assault outside the team hotel in Wellington following France's 14-10 defeat against the All Blacks on June 20.

And Fillon, in a move designed to take some of the heat out of the affair, told Key in his letter sent on Tuesday: "France's tour of New Zealand has been marked by the unacceptable behaviour of one of its players.

Bastareaud's original charge of being attacked and hit on the face by four or five men outside the hotel shocked New Zealand and led to an apology from Key.

But a police investigation found video evidence that the player had entered the team hotel on the Sunday morning uninjured and had gone into his room 25 minutes later.

Fillon told Key: "By his false statements, as a result of which you had to intervene publically, he seriously tainted the image of your country and its people."

Fillon said that he "regretted this incident" and added: "Our two countries share the culture of rugby.

"This sport has always allowed us to meet and to share a mutual respect. I hope that these sentiments will continue after this regrettable affair."

Bastareaud, who was on Monday admitted to hospital with serious psychological problems, received support Wednesday from the French players' union, Provale.

"We, professional rugby players, lend our friendship and support to Mathieu Bastereaud and his family," Provale noted in a statement.

"We solemnly demand that the media storm which nurtures doubts and fantasies ends immediately. We want above all that his privacy be respected and we hope that he makes a return to the pitch as quickly as possible."

The French Rugby Federation (FRF) president Pierre Camou meanwhile also offered his excuses to New Zealand over the affair that blighted France's All Black tour.

A FRF statement declared: "Pierre Camou, in the name of French rugby, presents his excuses to the New Zealand people and to the New Zealand (rugby) federation.

"To be an international carries with it responsibility as a representative of your country and your federation.

"The FRF is shocked that one of the French XV has lied. The New Zealand nation and the world of rugby can legitimately feel wounded by the player's initial statements which have also tarnished the image of French rugby."

Camou has contacted the FRF's disciplinary commission and has called for an inquiry into the episode.

Bastareaud returned home early from the tour to treat his facial injuries as the rest of the French squad travelled on to Australia and on his return issued an apology saying he believed he had to tell the truth following the media spectacle.

He said that instead of being assaulted he had in fact sustained the bruises to his face after a drunken fall in his hotel room.

He said he had invented the assault story to avoid being sent home by the French team management and upsetting his family, who are deeply religious.

Bastareaud, who had been due to go on a family holiday to the Caribbean this week, is expected to stay in hospital for at least a fortnight under observation.