If governments across the world fail to act, it will have dire consequences for the environment and generations to come.
Cutbacks and slow progress on policies to tackle climate change must be urgently reversed if the UK is to meet its new legally-binding net zero target, MPs have said.
The target to cut the UK's greenhouse gas emissions to zero overall by 2050 was passed into law earlier this year - but MPs warn it will not be met without new policies to boost clean growth.
The Commons Science and Technology Committee pointed to a number of areas where Government policy to support bringing in low-carbon tech had been delayed, cut back or had undermined emissions reductions.
They include cuts to grants for low emissions cars, the freezing of fuel duty while trainand bus fares have risen and the restriction and removal of policies to improve the energy efficiency of homes, a report by the MPs said.
Committee chairman Norman Lamb said the Government was not putting in place the policies that were needed to meet its climate targets, with the UK currently not on track to meet its goals into the 2030s, let alone net zero.
"We need to see the Government put its words into actions. We heard of cutbacks in various programmes and slow progress, which are incompatible with the UK's two upcoming, legally binding, carbon budgets - this is unacceptable.
"If governments across the world fail to act, it will have dire consequences for the environment and generations to come."
Meeting the target requires efforts to cut carbon emissions from heating systems, improve home energy efficiency, tackle vehicle pollution, support onshore wind and solar power and sustain nuclear power without growing the industry, the report said.
Meeting ambitions for virtually all cars and vans to be low carbon by 2050 will require 20,000 new registrations a week on average, compared to 1,200 ultra low emissions vehicles registered each week in 2018, the report said.
The committee joined calls for the Government to bring forward a ban on the sale of new conventional cars and vans planned for 2040 to 2035 at the latest, and for it to explicitly cover hybrid vehicles.
It also called for moves to tackle emissions from car manufacturing, and urged greater efforts to reduce vehicle ownership, boost public transport and car sharing, as well as walking and cycling.
The report also said the Government must commit now to large-scale trials of low carbon heating technology such as heat pumps, and replacing gas with hydrogen.
A policy to make new homes "zero carbon", which was scrapped before it was implemented in 2016, should be urgently reintroduced, and incentives are needed to encourage people to make energy efficiency improvements.
Ministers must support new onshore wind and large-scale solar power projects which have local backing, the report added.
And the Government should publish an easily-accessible, central guide for members ofthe public explaining what measures individuals and households can take to support the UK's emissions-cutting.
A Government spokesman said: "From transport to heating, electricity to agriculture, we are working to put in place the right measures to help us tackle global warming.
"We welcome the committee's report and will consider its findings.
"We are going further and faster to tackle climate change than any other major economy, having legislated for net zero emissions by 2050."
Emily Beament is the PA environment correspondent.