An eco campaigner staging a tree-top protest against the redevelopment of Oxford's Bonn Square has been threatened with court action.

Protester Gabriel had coped with temperatures as low as -1C for 36 hours.

He remained defiant after Jeremy Thomas, head of legal and democratic services at Oxford City Council, wrote to him yesterday threatening an injunction if he continues to trespass on its property.

Mr Thomas told the 34-year-old: "The council is the owner of the land in Bonn Square on which the tree is situated and has given you no licence or permission to occupy the land or climb the tree."

Gabriel, who refused to reveal his last name, constructed a makeshift shelter on the tree on Thursday morning before climbing into it to protest against a £1.5m makeover of the square.

Yesterday, he said: "I'm going to stay up here until they drag me down.

"Most people in Oxford support me. It's not right. It's the last bit of free space that we can sit on."

Gabriel said he used to sleep rough in the area and many homeless people had flocked to his side to support his cause.

About four rough sleepers bedded down at the foot of the tree last night and guarded the area while Gabriel came down for 25 minutes at 2am to go the toilet.

Other members of the public have also stopped by to pass him blankets, cakes and biscuits.

Steve Laughton, 30, of no fixed abode, said: "I heard my friend was up here so I brought him some toilet roll, a hat, scarf and gloves to keep him warm, and I'll continue to bring him what he needs for as long as he needs it."

Another friend, Brynie, 36, said: "I think there were four or five of us slept down here last night. I think numbers will grow as people hear about it more and more."

City council workers continued clearing the land and trees to the side of the sycamore tree which Gabriel is in yesterday.

At 10.45am police joined council officers to make the protester aware of the letter.

One Pc handed out two Section 27 notices to people drinking in the area.

The notices, made under the Violent Crime Reduction Act 2007, mean the drinkers are banned from returning to the area for 48 hours. Another five people were warned about their behaviour, a police spokesman said.

Passer-by Lavinia Walker, 27, from nearby Paradise Street, said: "I can see why he has taken a stand, but something needs to be done about that square.

"There are so many people hanging out there that drink that I get intimidated walking past on my own."

Ian Davis, 60, from Osney Lane, added: "I think he's doing a good thing. I'm surprised he's the only one up there."

A council spokesman said it was waiting to see how Gabriel responded to its request for him to leave.