The campaign group 38 degrees is asking its members to contact local council leaders to ask about their plans for parks, and will help them send follow-up questions in freedom of information requests.

The group said there was growing concern that councils, faced with swingeing budget cuts, are selling off parks and green spaces to try to make ends meet.

“Year after year park budgets are being cut, but too often the people who actually use them know little about the plans,” said Lorna Greenwood, the campaigns manager at 38 Degrees. “From fewer park rangers to deals with big companies that mean local people have to pay to use their parks, parks around the country are at risk. This investigation is about people across the country coming together to expose the truth so they can make their voices heard.”

More than 180,000 people submitted evidence to the communities and local government committee’s parliamentary consultation, which closes on Friday, calling on the government to make it a statutory duty for councils to protect and maintain the country’s 27,000 public parks. Separately, 322,000 people signed a petition calling for legal protection and 115,000 completed a survey, both of which were organised by 38 Degrees.

A report from the Heritage Lottery Fund this month said the UK’s parks risked falling into disrepair and neglect as a result of budget cuts. While 90% of families with children aged under five had used their local park at least once in the past month, the study said, 92% of park managers had had their budgets cut and 95% were facing further reductions.

Campaigners say the public needs more information as there is no central record of how much money is being spent on looking after local parks – or how many are at risk from corporate deals.

38 Degrees said the investigation would reveal which parks were most at risk and would allow people to put pressure on their local councils and MPs to protect parks in their area.

Greenwood said: “Parks aren’t just a nice to have. Thousands of people from wheelchair users to young families say they are absolutely essential for health and wellbeing. They’re part of our heritage.”