Some of America’s leading gun auctioneers have refused to sell the gun that neighbourhood watch volunteer George Zimmerman used to shoot dead teenager Trayvon Martin.

One described Zimmerman as “despicable,” while another compared the sale of the weapon to trading in Nazi memorabilia.

Zimmerman, who was charged with Martin’s murder but dramatically acquitted in 2013 under Florida’s controversial self-defence laws, contacted auctioneers with a view to selling the 9mm Kel-Tec pistol.

Cowan’s Auctions in Cincinnati and James D Julia Auctioneers in Fairfield, Maine, both said Zimmerman made enquiries about handing the gun over to them for sale.

Handout photo of the handgun that was used in the shooting death of Trayvon Martin

The 9mm Kel-Tec pistol was used to shoot teenager Trayvon Martin in 2012

James Julia said: “The man is despicable and I would have nothing to do with his gun,” while Wes Cowan said: “Morally and ethically, no, I wouldn’t do it.”

Martin was a 17-year-old black American student living on the gated housing estate Zimmerman was patrolling when the pair got into an altercation before the shooting.

The killing ignited a passionate debate in America over guns, the right to self-defence and black civil rights.

Trayvon Martin

Zmmerman insisted Martin attacked him and he shot him in self defence

Zimmerman, who is Hispanic American, insisted he was attacked by Martin and defended himself under Florida’s “stand your ground” law.

He told Orlando TV station WOFL this week that the gun was his to sell and he would not be “cowed” by critics.

An ad for the gun appeared on eBay and attracted false bids of up to $65m from bidders with names such as “Racist McShootFace,” though it is not known if the ad was genuine.

Antique firearms consultant Sean Rich said the negative publicity for an auctioneer should they agree to accept the weapon for sale would outweigh any profit.

“That’s one of the reasons I choose not to deal with Nazi material. You have to draw the line somewhere,” he said.