Campaigners and MPs have accused ministers of leaving vulnerable households in the cold, as new figures showed installations of insulation and boilers have sunk to their lowest levels since the government’s flagship energy efficiency scheme started six years ago.

Delays to legislation were blamed by fuel poverty campaigners for the fall, which coincided with households being hit by energy price hikes.

Just 2,557 boilers were installed in the last three months of 2018, 97% below the same period in 2013, the year the government’s Energy Company Obligation (ECO) scheme was launched.

Insulation of lofts and walls has also plummeted under ECO, which enables electricity and gas suppliers to use energy bill levies to upgrade the efficiency of homes, including those in fuel poverty.

There were 6,461 installations in the last three months of 2018, down 98% on the same period in 2010, according to government figures published on Thursday.

Fuel poverty charity National Energy Action said the government was allowing a “chronic public health crisis” due to the link between cold homes and early deaths.

Adam Scorer, the group’s chief executive, said: “Despite knowing energy efficiency saves money, carbon and lives, the number of insulation measures and boilers installed is falling off a cliff and very little support will have reached those most in need this winter.”

Rachel Reeves, Labour MP and chair of the business, energy and industrial strategy select committee, which is holding an inquiry into energy efficiency, said: “The government’s statistics underline the cold reality that the current rate of energy efficiency improvements is far too slow.”

The NEA said the crash in installs had happened because the government had created regulatory risk for firms by failing to pass legislation and issue guidance in time for the ECO’s scheme’s latest stage, which started in October.

Caroline Lucas, Green party MP and co-chair of the All-Party Group on Fuel Poverty and Energy Efficiency, said: “The government’s failure to insulate homes is a dereliction of its duty to vulnerable people.”

The UK’s climate advisers, the Committee on Climate Change, recently wrote to the energy minister, Claire Perry, to warn insulation levels under government schemes had fallen “very significantly” since 2013.

The CCC said on Thursday that gas boilers should no longer be fitted in new homes within six years, to ensure climate targets are met. Instead, new builds should stay warm using low carbon alternatives, very high levels of energy efficiency and timber frames.

A government spokesperson said: “To tackle fuel poverty and reduce energy costs, the ECO3 scheme prioritises energy efficiency measures, such as insulation, that deliver the best long-term results.

“We will continue installing boilers for vulnerable households whose occupants are unable to repair or replace their broken heating systems.”