More than 100 business leaders have warned Boris Johnson that his plans to tear up the planning system in England risk opening up protected land for development and may leave the UK in breach of legally-binding environmental targets.

In a letter sent to the prime minister on Friday, FTSE 100 bosses, academics and sustainability experts said that the proposals did not go far enough to ensure environmental objectives would be met.

The UK has pledged to become a “net zero” emitter of carbon by 2050 and has set in law a binding target to slash emissions by 78 per cent by 2035 compared with 1990 levels.

But that target risks being missed because of the government’s “siloed” approach to three of its core policy areas: housebuilding, infrastructure development and hitting environmental goals, according to Julie Hirigoyen, chief executive of the UK Green Building Council, which co-ordinated the letter alongside the Aldersgate Group, a green alliance of business and civic leaders.

“It doesn’t feel as though we have a high-level plan to achieve net zero. The planning system needs to be a key part of that,” Hirigoyen said.

“The current planning system is definitely not going to meet the pace of change we need to deliver net zero and sustainability targets,” she added. But while the government’s ambition and initiative on reform was welcome, references to sustainability were scant in its 84-page white paper, she said.

“There’s a big emphasis on speeding up planning. But a note of caution: that could come at the expense of net zero, biodiversity or community involvement.”

Unveiled in August last year, the government has billed the proposals as the most significant reforms of the planning system in more than 70 years.

“Not more fiddling around the edges, not simply painting over the damp patches, but levelling the foundations and building, from the ground up, a whole new planning system for England,” was how Johnson described the package last year.

But key elements of the proposals may come unstuck before they become law, having met staunch resistance from campaigners and Conservative MPs.

One of the most controversial proposed reforms is a plan to scrap the current planning decision making process, in which applications are decided on a case-by-case basis at a local level. Under government plans, that would be replaced by a ‘zonal’ system, in which swaths of land would be earmarked either for development or protection.

Opening up land without appropriate protections risked “inappropriate development” cautioned signatories of the letter, which include real estate companies British Land, Berkeley Group and JLL, engineering companies Arcadis and Buro Happold, institutional investors including Legal & General Investment Management and Thames Water, the utility company.

Those companies “want a clear investment landscape based on high environmental standards, said Nick Molho, chief executive of Aldersgate Group. “You don’t want to invest in a big infrastructure project and find the rules have changed five years down the line,” he added.

In a separate report published on Thursday, the House of Commons Housing, Communities and Local Government select committee said the proposals for a zonal system lacked “the necessary detail” and should be reconsidered.

Clive Betts, a Labour MP and the committee’s chair, said “the government’s aim of developing a planning system that enables buildings to be built more quickly and with greater input from local communities is welcome, but it is far from clear how the current proposals will achieve this.”