More than 40 councils in coastal areas of the UK have demanded a £1bn “kick-start” from the government to help recover from the impact of coronavirus.
In a letter to the chancellor, they say the money could create almost 74,000 jobs by developing zero-emission ships and offshore wind farms.
This would help “economically at-risk” communities, they add.
The government said it was supporting “millions of firms” through the pandemic and “continuing to innovate”.
In his speech to the virtual Conservative Party conference on Tuesday, Prime Minister Boris Johnson promised to make the UK a “world leader” in green energy.
He announced £160m of investment in ports and factories to increase electricity generation from offshore wind.
But the trade group Maritime UK, which coordinated the letter, is calling for a “more ambitious” approach when Chancellor Rishi Sunak unveils his Comprehensive Spending Review later this year.
Ships could be developed that are powered by hydrogen, ammonia or biofuels, it is argued.
The letter says a £1bn investment in decarbonising the UK’s sea transport sector would directly create 15,200 jobs and add a further 58,400 in the supply chain.
It warns: “But without investment, this opportunity will be missed, and the UK will risk losing its position as a world leader in maritime.
“Many other countries around the world are already acting to support the decarbonisation of their maritime industries, and the UK government must do the same.”
The leaders of 41 coastal councils have signed the letter, along with five mayors.
Maritime UK director Ben Murray told the BBC that, without the investment, the UK “cannot reach” its commitment to lower net greenhouse gas emissions to zero by 2050.
In its Clean Maritime Plan, published last year, the government said it wanted “zero-emission-capable” ships to operate in UK waters by 2025.
In July, the charity Social Investment Business said coastal communities, many of which depend on seasonal tourism, had taken “one of the biggest economic hits” from the coronavirus crisis.
It added that they had a “large concentration of businesses and employees in sectors that were closed during the lockdown” and had “experienced some of the largest drops in local spending, as well as the highest rises in unemployment”.
A Treasury spokesperson said: “Our support for business has reached, and continues to reach, millions of firms. The Job Support Scheme is designed to protect jobs in businesses facing lower demand over the winter due to Covid, and is just one form of support on offer to employers during this difficult period.”
They added that businesses could “still access our loan schemes, now extended, defer VAT payments previously due in March, and benefit from business rates holidays, a moratorium of eviction for commercial tenants and the Statutory Sick Pay Rebate Scheme”.
“We’re also continuing to innovate in supporting incomes and employment through our Plan for Jobs announced in July, helping employees get back to work through a £1,000 retention bonus and creating new roles for young people with our Kickstart scheme,” the spokesperson said.