CONCERNED councillors will write to Westminster amid fears 'unrealistic' housing targets could see green spaces in Portsmouth lose protection from development.
A new government formula could require Portsmouth City Council to build over 800 homes every year, or face penalties.
This is a significant jump from the current local plan which is set at 584 houses annually for the city.
At full council this week councillors voted unanimously to lobby the housing secretary to keep the target as low as possible.
Council leader, Cllr Gerald Vernon-Jackson, said: 'We have a local plan which is based on the number of houses we think we need to build to meet the needs of the population in Portsmouth which is around 500 a year. The government is pushing us and has given us a target of over 800 a year until 2036.
'We don't have unlimited land in Portsmouth. The only way all these homes can be built is if we cram and cram and cram. It is entirely unrealistic.
'At the moment we are building about 400 new homes a year. The target is over double that. If we don't achieve that target government has threatened that there will be consequences. Protection on some areas of land in Portsmouth could be removed.
'We need to make sure quality of life for people in this city is protected. I think we need to be speaking with one voice if we possibly can to tell the government we can accept and achieve realistic targets.'
Cllr Darren Sanders, the council's housing boss, was concerned about the risk of losing protection on land. He said: 'If we get punished it's not because of something we did wrong but because of something we could not do. That in my mind is unfair and wrong.'
The motion had cross-party support. Tory leader, Cllr Donna Jones, said: 'It's all very well and good when you're setting these policies when sat in Whitehall and don't understand local spaces.
'We are the only island city in the UK. For us to be building outwards would mean reclaiming the sea which would be extremely expensive.'
Her peer, Cllr Luke Stubbs, added: 'It is a national way of setting a target. I don't think we are going to end up with a target in the 800s, at least I hope not.
'What worries me most is that we can lose planning powers if we meet our target.'