City centre campaigners have pledged to fight on in their battle to protect precious green areas in the heart of Salisbury so that residents can enjoy them for generations to come.

Two years ago, families living in the middle of Salisbury formed an action group in a bid to legally protect what remains of their ancient green spaces in the face of increasing threats from development.

But they suffered a set-back after a planning inspector rejected their case for an important swathe of open space to be declared a town green, which would have protected it from any development.

At an inquiry last year the Salisbury Town Green Group argued that parklands and open spaces surrounding the city's controversial Bourne Hill civic centre complex should become a town green.

Their case was built on the grounds that local people had been using the green areas as a recreation space for many years.

The group insisted it was their right to continue to do so without fear of further sections of the important open space being "pinched" by developers.

The inspector disagreed, saying that residents' use of the parkland for walking their dogs or simply enjoying a stroll on a sunny afternoon was not "as of right".

Now the group will challenge that statement when the new Wiltshire unitary authority – which comes into being on April 1 and has the final say in the matter – considers the issue on April 22.

The town green group has submitted a statement to councillors arguing that the report did not appear to give equal weight to all the evidence.

Members are also urging the regulatory committee to look closely at the history of the public use of the city's green spaces. The inquiry said residents had used the land for recreation since 1927.

During the inquiry the group said the encroaching development of the land had been " at the very least a breach of the trust".

Group chair Victoria Morton said: "In the end, what matters is that this land is protected for future generations. That has been our sole aim from the very beginning."

Two years ago there was outrage in Salisbury when the council closed the city's Georgian Secret Garden with the aim of bulldozing it to make way for a huge new civic centre.

The 300-year-old oasis was later saved after a Lib-Dem and Labour alliance ousted the Tory administration and a modified version of the controversial Bourne hill civic centre was approved.

Local residents were so shocked at the threat to the Secret Garden that they decided to do something to protect it and other important open spaces which offer a retreat from the hubbub of the city.

Mother-of-two Jan Bradford said: "When the Secret Garden was threatened we thought that nothing was sacred. If they could build on that they could build anywhere. We had to do something."

The group initially focused on the green areas around Bourne Hill and its application for the land to be registered as a town green was made to Wiltshire county council in March 2007.

Nine months later councillors resolved to hold a non-statutory public inquiry, meaning the inspector's decision would not be final.

The group is also looking to preserve other green spaces such as Wyndham Meadow, St Edmunds churchyard and Greencroft.