Sacha Baron Cohen is suing a US cannabis dispensary for allegedly using his comedy character Borat on its advertising.

The 49-year-old British film star is seeking damages of at least $9m (£6.5m), according to a lawsuit filed in the US state of Massachusetts.

He is accusing Solar Therapeutics of copyright infringement and false advertising.

The lawsuit alleges that the advert featured Baron Cohen as Borat, giving the thumbs up with the words “it’s nice!”.

It was placed on a busy highway in Massachusetts.

Borat is one of Baron Cohen’s most famous characters – a bumbling fictional Kazakh journalist who offends almost everyone he meets in two hugely popular films.

Baron Cohen’s lawyer said that Solar Therapeutics had taken “a gamble”, hoping the actor would not see the advertising.

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According to the Hollywood Reporter, the lawyer sent a cease-and-desist letter to the cannabis company.

The billboard had been taken down but the company refused to compensate Baron Cohen for the unauthorised use of his image.

Solar Therapeutics has not commented.

In the lawsuit, Baron Cohen said he has never used cannabis, as it is an “unhealthy choice”.

He also said he had refused to advertise any product in the US and UK “despite countless opportunities to do so”, due to fears it would “weaken his credibility as an actor and a serious social activist”.

The lawsuit said that he once refused a £2.9m offer to appear in a car advert.

Despite several US states giving cannabis the green light, it is still illegal under federal law.