Blackpool and Walsall have been identified as the two areas of the country most in need of new free schools, as the government prepares to restrict where the controversial institutions can be opened.

The New Schools Network has launched a “map of need” tool, to help proposers of new free schools schools with their bids.

According to the tool, the areas most in need of good primary free schools are Walsall, Leicester, Bury, Kirklees and Bradford.

Blackpool, Leicester, Oldham, Sandwell and Darlington are highlighted as the areas with the greatest need for new secondary free schools.

Our map will help ensure that those groups coming forward to set up them up focus their efforts in the areas of greatest need

Run by the right-wing journalist Toby Young, who founded the West London Free School, the New Schools Network is an advocacy group funded by the government to promote the programme and assist with applications.

Free schools are a form of school opened via applications to central government, and have been a pivotal government policy since 2010.

Since last summer, it has been the government’s policy to wave applications through as long as proposers can demonstrate a “social need” or “significant demand” from parents.

But Justine Greening last month outlined a change to the government’s approach to the application process that will effectively restrict where new projects can be launched.

The government will invite a new wave of mainstream applications in early 2018, “with a particular focus on enabling more challenging areas to feel the full benefit of the programme”.

The New Schools Network’s online tool uses national data on current school capacity, pupil-number projections and information about school performance to calculate what it calls an “NSN score”. This is then used to rank areas by their apparent “need” for new free schools.

It allows users to see where increased in recent years, and how it is forecast to grow in the future. The NSN says the data can be downloaded by proposer groups to use in their free school applications to the Department for Education.

According to Young, who took over as director of the network from Theresa May’s former chief of staff Nick Timothy in January 2017, the new tool will allow prospective free school groups to “identify the areas where their efforts will have the greatest impact”.

“Free schools have become an established part of the educational landscape, opening up across the country to address educational underperformance,” he said. “As we continue to build new ones, our map will help ensure that those groups coming forward to set up them up focus their efforts in the areas of greatest need.”