A petition has been launched to fight plans for hundreds more homes in south Bristol.

The people behind it fear that the number of new homes at Hengrove Park will more than double from 690 to 1,450 during the next 18 years. And they claim that if this number of homes is built, then it puts the park at risk as a treasured open space.

They also believe it will mean blocks of flats to accommodate so many homes.

Liberal Democrat Councillor Tim Kent, who represents Whitchurch Park, together with councillors Mary Sykes and Jos Clark, who both represent Hengrove, have now started the petition to save the park.

Mr Kent said the figure of 1,450 homes is buried in a report to the city council in June by the West of England Partnership. It can be seen halfway down a table on page 49 of the 148-page report.

Mr Kent said: "We always knew that some homes would be built at Hengrove Park. A referendum was carried out some years ago among local people to find out how many homes they felt should be built. The result of the referendum was 500, but since then, the figure has crept up to 690. But now that figure has jumped to 1,450, which is a massive difference."

He said the plans for Hengrove Park which were published in 2005 show that 11 hectares (27 acres) has been zoned for new homes. He said: "I can't see how they can build this many homes without building five and six-storey blocks of flats. The only alternative is to use more of the park."

Some of the parkland is already earmarked for a multimillion health complex, which will include a leisure centre with swimming pool and a new hospital. Another part is designated as a site of special scientific interest and cannot be built upon.

Mrs Sykes, who has been tracking plans for Hengrove Park for years, said: "The goalposts keep changing which means it's very difficult to keep up-to-date with what is planned.

"The trouble is, everyone thinks of Hengrove Park when they need somewhere to build something."

The report which shows the 1,450 figure is in a policy document called an MAA (Multi-Area Agreement) by the partnership to the city council's ruling cabinet on June 29. An MAA is a voluntary agreement between two or more councils and the Government to promote economic growth in a specific area.

The partnership is a body which represents the four councils in the former Avon area, including Bristol.

The cabinet approved the MAA, subject to detailed adjustments agreed by council leader Barbara Janke.

Mr Kent said a number of councils were challenging the Government in the courts over housing quota numbers.

He said the cabinet might be urged to push for their own legal challenge to stop so many homes being built in Bristol.

The councillors are leafleting thousands of homes in the area and planning to organise a public meeting.

Partnership spokeswoman Julia Dean said they did not produce the figures for the report – they were provided by the council. She said the four councils in the partnership have objected to the housing quota numbers and were therefore the subject of ongoing discussions.

Lib Dem Cabinet Councillor Dr Mark Wright, who is in charge of the council's housing department, said: "We are examining where these housing numbers have come from. We are very sure that we want to keep this park as big as we possibly can."