City for People is made up of environment and transport professionals, Renters United and Students' Association members.
Its spokeswoman Isla Stewart gained traction on the issue when she wrote an opinion piece published by The Spinoff titled: "Keeping Wellington's character means keeping people in cold and mouldy homes".
"Those heritage groups have a very loud voice and we have to provide an alternative", she told the Herald.
The group supported the spatial plan as it stands, she said.
"We have heard a lot from people who say they want to protect the character of old houses, and what we are saying is that the character of a city comes from its people.
"Without a credible plan for new affordable homes, a whole generation of Wellingtonians is at risk of being forced out from the central city into new suburbs sprawling north, and spending hours every day in traffic jams."
Stewart acknowledged KWC as bringing a view to the table and was happy to work with them.
But she said the spatial plan already presented a solution with a compromise, because it still protected some heritage.
She said the unfortunate thing about a lot of these character suburbs under the current status quo was that they were all inner suburbs with very low height limits.
"People need to be where the jobs are, you can't force people to commute hours in the city paying really high transport costs - that defeats the purpose of affordable housing.
"If we don't allow development in these inner suburbs they're going to be destroyed by congestion from people coming in from a sprawling urban area."
KWC spokeswoman Felicity Wong is also the chairwoman of Historic Places Wellington.
She welcomed the campaign and further discussion about affordable housing and increasing supply.
"We want housing plus heritage, we don't want housing instead of heritage, nor do we want heritage instead of housing."
Wong said there was a huge amount of low value commercial property in Te Aro and Newtown that should be developed for housing.
"I don't actually live in any of the heritage suburbs but I appreciate them, so I am not a NIMBY. If I did live in Mt Victoria, I would be a YIMBY.
"I would be saying 'yes develop all the way along Kent and Cambridge Terraces', which is just a stone's throw away from Mt Victoria."
Wong doubted freeing up space on Mt Victoria would equate to affordable housing, which wasn't the most profitable option for developers.
"There will be boomers like me moving into unaffordable apartments.
"The winners are the cashed up boomers again and the losers are the young folk and heritage."
At the moment there are parts of the city identified as character areas, like Thorndon and Mt Victoria.
A resource consent is required to demolish any pre-1930s buildings in these areas.
But the spatial plan proposes to re-jig the boundaries by creating "sub-areas".
Anything outside of the designated sub-areas would no longer be subject to the demolition controls, because they're considered areas that don't exhibit a cohesive streetscape character, or are where character has been compromised.
Basically, protection would become smaller and more targeted to enable denser development within the broader character area.
Building heights outside of the sub-area could be between four and six storeys.
