The think tank found that workers in seaside towns earn almost £5,000 less than employees elsewhere in the country. People in coastal areas can also expect to die earlier than people who live inland, with the latest data showing a growing “death gap” between seaside populations and the rest of Britain.

The SMF said the figures showed that many coastal towns have “missed out” on much of the economic growth Britain has experienced since the financial crisis and need a special package of help from the government.

In a report titled Falling off a cliff?, the SMF analysed official statistics and found that the gaps between local authority areas on the coast and the rest of the country are widening significantly.

While most of the country saw wages rise from 2017 to 2018, the SMF calculated that coastal workers suffered falling incomes.

In 2017, non-coastal workers had an average salary of £29,291, rising to £30,592 in 2018. For coastal workers, the average wage was £26,098 in 2017, falling to £25,906 in 2018. This means the coastal wage gap has risen from £3,193 to £4,686.

The SMF calculated that long-term economic decline means that many coastal towns are poorer than they were before the 2007 financial crisis hit. A total of 32 local authority areas with significant coastlines had smaller economies in 2017 than they did in 2007. Of those areas, 24 voted to leave the European Union.

The SMF also found that coastal areas are experiencing a decline in health relative to the rest of the country, meaning people living by the sea face shorter lives.

In the early 2000s there was no significant life expectancy gap for men born in coastal communities. But those born today can now expect to live half a year less than those in other parts of the country. Non-coastal men have a life expectancy of 79.3 while men who live in coastal authorities can expect to live to 78.8.

Non-coastal women have a life-expectancy at birth of 83 years, according to SMF analysis of the latest official statistics. But coastal community women can only expect to live to 82.6 years, a difference of almost five months.

The SMF report is the latest in a string of warnings that coastal towns are falling further and further behind as traditional employers like tourism and fishing fade and are not being replaced with newer, higher-paying work.

The think tank called for the government to help seaside communities including tax incentives for employers in higher-paying sectors to locate in coastal areas, and new “Powerhouse” devolution deals to allow planning at a regional level.

Scott Corfe, SMF research director and the report’s author, said: “Coastal areas are sadly falling further behind the rest of the country. That means people there are poorer and even die younger than people elsewhere in the UK. Gaps like that are unfair and should be addressed.

“Many coastal areas are still poorer now than they were before the financial crisis in 20007. In the context of the Brexit debate, it’s notable that most of those areas voted in favour of leaving the European Union. Prime Minister Boris Johnson has said he wants to help ‘forgotten’ parts of the country. Coastal areas where incomes and lifespans are falling certainly fit that description.”