Over the past year, it says, the government has delivered just one of 25 critical policies needed to get emissions reductions back on track.
Meanwhile, action to prepare our homes, businesses and natural environment for a warming world is less ambitious than it was ten years ago.
A Government spokeswoman said: "As the CCC recognises, we are the first major economy to legislate for net zero emissions, have cleaned up our power sector, cut emissions faster than any G7 country while growing the economy, championed adaptation and set a strong example for other countries to follow. For transport, that means transformative investment in a charging network for electric cars, bringing forward the end date for polluting petrol and diesel engines to 2030, a rolling programme of rail electrification and a national strategy for buses that makes Britain a leader in low carbon public transport".
Energy Networks Association's Chief Executive, David Smith said the United Kingdom must seize momentum from the establishment of the net zero target to deliver the necessary action needed.
Lord Deben, CCC chairman, said: "It's time for the Government to show it takes its responsibilities seriously".
"The Government is not yet addressing adequately all of the climate risks it has itself identified as critical - including from surface water flooding and the impacts of high temperatures on health" Baroness Brown said.
As the United Kingdom prepares to host next year's global climate summit, the Government has a window to demonstrate its commitment to addressing these responsibilities. "The effects of climate change are already being felt in the United Kingdom".
The CCC is additionally using its report as a call to action for the UK's next Prime Minister, arguing that they must work closely with the First Ministers of Wales, Scotland and Northern Ireland to ensure "embedded" and joined-up progress.
All biodegradable waste should be banned from landfill by 2025, if the United Kingdom is to reach "net zero emissions" by 2050, according to the Committee on Climate Change's (CCC) newly published report. It notes that without a "simple and investable" set of laws, the private sector's shift to low-carbon technologies is likely to be inefficient, adding that Ministers are likely to risk a backlash if low-carbon policies, products and services aren't designed around the needs of the public.
It says United Kingdom action to curb greenhouse gas emissions is "lagging" far behind what is needed, even to meet previous, less stringent, emissions targets. Over half of the emissions cuts required to reach net zero require people to do things differently. Such a move, the CCC claims, could help conserve soil, protect endangered habitats and manage flood risks without the need for costly and high-carbon physical infrastructure.
"The effects of climate change are already being felt in the United Kingdom".
He said Britain has a 12-18 month window, ahead of next year's global climate conference which it hopes to host, to get policies in place to make the target a reality and ensure the country's credibility at the event. Key opportunities need to be seized over the next 12 months.
Reward farmers who are working to improve the natural environment. The Agriculture Bill will lead to a new payment system for farmers after the United Kingdom leaves the EU.
Stuart Hayward-Higham, technical development director, SUEZ recycling & recovery United Kingdom, said the United Kingdom will have only two years after the planned legislative timeframes for consistent collections, EPR (Extended Producer Responsibility schemes ) and DRS (Deposit Return Schemes) in which to deliver "affordable and viable" alternatives - which can often take five years or more to obtain planning, finance and to be constructed.
Take steps to protect people from the unsafe effects of overheating in homes, schools, care homes and hospitals, including through the current review of Building Regulations.
'We'll set out plans in the coming months to tackle emissions from aviation, heat, energy and transport as well as further measures to protect the environment from extreme weather including flood protection, tree planting and peatland management, ' the spokesperson said.
The UK government is failing to act on climate change and will struggle to meet its new 2050 net zero carbon target unless urgent action is taken, the Committee for Climate Change (CCC) has warned.
"We know there is more to do and legislating for net zero will help to drive further action". It is time now for government to get on and make it happen.