The government is to double spending on flood defences in this week’s budget after recent storms caused havoc across the country and drove thousands from their homes.

The chancellor, Rishi Sunak, will announce an increase from £2.6bn to £5.2bn in spending on flood defences between 2015 and 2021. He will tell MPs that the money will give protection to 336,000 homes in England and allow 2,000 new flood and coastal defence schemes to be built.

The announcement will be a centre-piece of Sunak’s first budget, which he is determined will focus not only on measures to combat the spread of coronavirus but also on national infrastructure to reduce risk of flooding in England by 11% by 2027.

This follows grave warnings from scientists who have demanded far greater investment and Boris Johnson’s aim to “level up” the country.

Ministers said the extra spending would reduce the needed planning for future disasters, and warned that extreme weather would become far more regular. Last month Storm Ciara and Storm Dennis swept across the country bringing rain and wind gusts of up to 97mph and triggering more than 190 flood alerts.

More than 500 properties were flooded and about 25,000 homes left without power. A week later Storm Jorge followed, which in some areas caused more than a month’s rain to fall within 24 hours.

But Sunak – who is expected to delay announcing a far wider national infrastructure strategy until the summer or autumn – is coming under intense pressure to spend much more on the environment and the climate emergency to ensure the UK meets its climate targets.

On Sunday, on the eve of the budget, the Institute for Public Policy Research thinktank publishes analysis showing an additional £33bn a year must be spent on measures to tackle the climate crisis if it is to meet its target of cutting carbon emissions to zero by 2050. Investment in low-carbon transport alone – including more infrastructure for charging electric vehicles, improved railways and better facilities for cyclists – would have to rise by £12bn a year, and spending on low-carbon homes and other buildings would need to be increased by £10bn annually.

The huge sums would not only help tackle climate change but would also deliver an economic boost and help Johnson deliver on his ambition to “level up” the country, IPPR says.

Last summer the Tory government signed into law a commitment requiring the UK to bring all greenhouse-gas emissions to net zero, replacing the previous pledge to reduce them by at least 80% compared with 1990 levels.

Former Labour leader Ed Miliband, a co-chair of IPPR’s Environmental Justice Commission, said the budget needed to put climate change at its heart.

“This will take investment, but making these decisions will create hundreds of thousands of jobs, improve our natural environment, cut air pollution and make Britain a better place to live. It makes economic and environmental sense. The time to act is now.”

In order to hit net zero within 30 years, the UK will need to be running on renewable energy with industry using mostly carbon-free processes. All homes and other buildings will have to be fully insulated and public transport will need to be greener, and more efficient.

Currently the government spends around £17bn a year on measures related to the climate and environment which, the study shows, would not even be sufficient for the government to meet its previous target of an 80% reduction in greenhouse-gas emissions by 2050. IPPR calculates that it would need to spend an additional £11bn just to meet that previous target.