Business leaders from across East Anglia have demanded the two candidates to be prime minister "properly invest in the East" to benefit the whole country.
In letters to foreign secretary Liz Truss and former chancellor Rishi Sunak, industry chiefs called on the government to upgrade the rail network and develop "coherent" plans for the life sciences and energy industries in the region.
Bosses at brewery firm Adnams, property firm Jaynic, West Suffolk College, the Institute of Directors and the Federation of Small Businesses have signed the letters. All of the signatories are founding members of the Eastern Powerhouse – a business-led group seeking better investment in the East of England.
Eastern Powerhouse bosses estimate that if the East was put on par with the south-east, it would deliver an extra £31.2billion a year in GDP for the national economy – and an £11.5bn in tax for the exchequer.
Dr Andy Wood, chief executive of Southwold-based Adnams, said: "East Anglia has so much economic potential that can be released through appropriate and timely investment in our region.
"For so long we have been overlooked in favour of other areas. Successive governments have missed out on all that the East has to offer and the wider UK is poorer for that.
"From food and farming to renewable energy. From life sciences to tourism we offer a great return on investment for government."
James Palmer, chairman of Eastern Powerhouse, said: "The huge disparity in UK regional investment is not the result of a needs-based allocation of funds, nor is it assigned based on expected return on investment.
"This is why the East is so often left out of the funding party, despite the considerable benefits that would accrue for the whole UK if the gap were closed.
"The members` message to the candidates is therefore simple: properly invest in the East as Prime Minister, and it will pay dividends in terms of all your other levelling up plans."
The business chiefs' intervention comes as Mr Sunak and Ms Truss unveiled what they had planned for East Anglia ahead of a hustings event in Norwich.
Ms Truss's plan cited several specific projects in Norfolk, but Suffolk was only mentioned in passing with regard to the striking workers at the Port of Felixstowe.
Mr Sunak pledged to fix the Norfolk and Suffolk Foundation Trust and rebuild West Suffolk Hospital, assess the case for improvements at Haughley Junction and look into "innovative and alternative solutions" to the controversial East Anglia GREEN line of pylons.
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