Rachel Reeves has been accused by environmental experts of putting the climate at risk with high carbon projects including the expansion of Heathrow airport.

The chancellor made airports the central focus of her plan for growth, despite having previously promised to be the first green chancellor and having extolled the benefits of green growth.

Environmental leaders have asked her to recommit to green growth, such as the renewable economy and green public transport, rather than expanded aviation and new roads.

Dale Vince, the founder of Ecotricity and a major donor to the Labour party, said: “New runways are a mistake; we don’t need them. This is the old economy, it grew 0.1% last year while the green one grew 9%. This is where the biggest opportunity for growth is, and it’s sustainable in all senses of the word. That’s the right kind of growth.”

Reeves did commit to a rail project, promising to create what she described as “Europe’s Silicon Valley” between Oxford and Cambridge, and giving support for a railway between the two university cities.

Shaun Spiers, executive director at the thinktank Green Alliance, said: “The chancellor is right to focus on economic renewal, but we cannot have growth at any cost. The economic case for bigger airports and new roads is highly questionable, and it’s crystal clear that pushing ahead with these will fly in the face of the UK’s climate targets. Rachel Reeves recognises that the low carbon economy offers ‘the industrial opportunity of the 21st century’; we should grasp this rather than chasing high-carbon, high-risk projects.”

Dr Doug Parr, head of policy at Greenpeace UK, suggested other growth-boosting measures the chancellor could adopt instead: “It’s not a ‘growth at all costs’ approach that will get us to a better economic future. Instead of picking up any old polluting project from the discard pile, the chancellor should focus on industries that can attract investment and bring wider economic and social benefits.

“These include upgrading our power grid, railways and housing while growing the renewables revolution and spearheading innovation in green steel, electric vehicles and batteries.”

Reeves did say the airport would not go ahead without meeting climate objectives: “We will then take forward a full assessment through the airport national policy statement. This will ensure that the project is value for money, and our clear expectation is that any associated surface transport costs will be financed through private funding, and it will ensure that a third runway is delivered in line with our legal, environmental and climate objectives.”

However, the Climate Change Committee, the independent watchdog tasked with ensuring the UK meets its legally binding net zero target by 2050, said in its sixth carbon budget that there could be no new airport expansion unless there were significant reductions in carbon intensity in other areas of the economy such as road transport and agriculture. Otherwise, the emissions would overshoot what is required to keep the UK within its carbon targets.

The seventh carbon budget will be published next month, and some have said decisions on airport expansion should have waited until it was released.

On Tuesday in parliament, the Green MP Siân Berry asked the transport minister Mike Kane: “Can the minister explain why we are hearing trailed announcements of multiple airport expansions, in the month before new advice from the Climate Change Committee is delivered? The committee could not have been clearer in previous reports that without a framework to manage aviation demand, we should not expand airports.”

Research from the New Economics Foundation suggests airport expansions would in effect cancel out the carbon savings of the government’s clean power plan, and backbench Labour MPs have complained that new runways will bring air and noise pollution to their constituents.

Alethea Warrington, head of aviation at the climate charity Possible, said: “Clearing the way for new runways is economically illiterate and sets our climate on course for a crash landing. The chancellor wants to boost growth, but new runways won’t strengthen our economy. Bigger airports will only benefit a tiny group of frequent flyers, while worsening the UK’s massive tourism deficit.

“There is no conflict between a safe climate and a strong economy. The chancellor should rethink these dangerous and self-defeating plans, and instead invest in the day-to-day connectivity provided by affordable, reliable, electrified buses and trains.”

Other plans outlined by Reeves in her speech include the Environment Agency lifting objections to build 4,500 new homes as well as schools and leisure facilities around Cambridge, nine new reservoirs, including the new Fens reservoir serving Cambridge, and the Abingdon reservoir near Oxford, and improving the A428 to reduce journey times between Milton Keynes and Cambridge.

She also vowed to reduce regulation in order to get infrastructure projects built, but experts have criticised this. James Alexander, the CEO of the non-profit UK Sustainable Investment and Finance Association, said: “Not all regulation is anti-growth. The UK stands to gain more from maintaining and furthering our leadership posture in sustainability, especially at a moment where other major economies risk alienating green investment by signalling regressions on climate ambitions.”