More than 100 protesters held a demonstration in the centre of Bristol to fight plans to build thousands of new homes on the green belt surrounding the city.

Members of a number of groups set up by residents in areas threatened with the loss of protected land gathered on Harbourside to voice their protests.

From Dundry, Whitchurch and Long Ashton to Shortwood, Siston and Warmley, they travelled to the Architecture Centre, where recently unveiled plans for a new town of 10,000 homes south of Long Ashton have gone on display.

Developers of the £2.5-billion Ashton Park project said the town would accommodate 25,000 residents and boast six schools, two "district centres", shops, community centre and a business park.

But the growing number of people fighting to save the green belt said if allowed, it would be just a taste of things to come for other areas.

Under proposals contained in the controversial South West Regional Spatial Strategy (RSS), more than 117,000 new homes will be built in the former Avon area by 2026 if given approval.

They include 38,500 for Bristol, 32,800 for South Gloucestershire, 26,750 for North Somerset and 19,300 for Bath and North East Somerset.

The document has put huge areas of countryside under threat and the reaction from the public has been so great – some 35,000 people from the region took part in the consultation – that the Government's response is not expected until later this year.

Land designated as green belt is usually found around towns and cities such as Bristol, forming an area where development is not normally allowed in order to prevent urban sprawl.

Campaigners are determined to protect it and want a re-think on moves to concrete over the green space.

Pip Sheard, of Bristol Friends of the Earth and Transport for Greater Bristol Alliance, said protest groups had formed to highlight the sheer scale of the development that threatened the countryside.

She said people at the demonstration lived in Bristol, North Somerset and South Gloucestershire and were joined by others from Bath and Cheltenham.

She said: "We have people working together from all over the West of England opposing the Government's high growth in housing targets."

She said the RSS was "loathed" but the development juggernaut was already on the road and it was vital for people to work together to stop it.

Jacquie Stephens, of the Save Warmley and Siston Green Spaces group, addressed the crowd and said it was "fantastic" that they had answered the rallying call to protest.

She said: "It shows that people power is important. We don't think there was a proper consultation on the RSS and we are trying to get a judicial review."

Chris Pope, of Dundry Residents' Action Group (DRAG), told the campaigners: "The exhibition that is on here today represents the first phase of the RSS and its intention to rob Bristol of the green belt.

"This development will set a precedent, If it succeeds, then others will also succeed. What happens with this one will affect you all."

Mary Walsh, of the Protect Whitchurch Green Belt Alliance, said: "We are just a small village but in the 60s, Bristol built thousands of houses around us. Now we have just one fillet of green left and we want to save it."

The demonstrators also heard from Ron Morton, of the Shortwood Green Belt Campaign, who said the protest was necessary because no-one in Government was listening to local people.

He said: "I want an opportunity to talk to the ministers behind these plans to tell them what's wrong with them."

DRAG spokeswoman Debbie Nicholls said she was pleased with the number of people who turned up for the event.

She said: "People have come a long way to give us their support. All the action groups are bonding together to support everyone – it's the only way forward.

"If we can show strength of numbers, hopefully the Government will start to take notice."

The Ashton Park scheme has been unveiled by developer Land Trust for a site between the A38 at Dundry, near the Barrow Tanks, right down to the A370 Long Ashton bypass and would provide nearly all the new housing proposed in the RSS for the south-western edge of Bristol up to 2026.

But campaigners are angry it was put forward before a decision on the RSS was made.