The UK's coastal communities are among the country's worst off for earnings, employment, health and education, a report for the BBC has found.
The Social Market Foundation said the economic gap between coastal and non-coastal places has grown.
Average wages are £3,600 a year lower in these "pockets of deprivation", according to the think tank.
Meanwhile, the minister for coastal communities has announced £40m in funding to help coastal areas.
The report, produced for BBC Breakfast, found that five of the 10 local authorities in the UK with the highest unemployment rate for the three months to March 2017 were coastal.
These were Hartlepool, North Ayrshire, Torridge, Hastings, South Tyneside and Sunderland.
It also found those in employment in coastal areas were likely to be paid less.
Of the 98 local authorities on the coast, 85% had pay levels below the UK's average in 2016.
In terms of health, 10 of the 20 local authorities in England and Wales with the highest proportion of people in poor health are coastal: Neath Port Talbot, Blackpool, Bridgend, Sunderland, Barrow-in-Furness, Carmarthenshire, East Lindsey, South Tyneside, County Durham and Hartlepool.
And the two local authorities in England and Wales with the smallest proportion of over-16s holding level four and above qualifications [certificates above A level] are Great Yarmouth in Norfolk and Castle Point in Essex.
Report author, SMF chief economist Scott Corfe, said a lack of local job opportunities and poor transport links contribute to badly-performing economies.
There is currently no official definition of a coastal community, which the SMF believes is a problem.
For its analysis the SMF defined them as a local authority area with a coastal border.
"Despite the evident social and economic problems these places face, there is currently no official definition of a 'coastal community'," Mr Corfe added.
"The government needs to do more to track - and address - economic problems in our coastal towns."
The SMF warned that some areas - particularly in the South East - "are pockets of significant deprivation surrounded by affluence - meaning their problems are often overlooked by policymakers".
The report found the economic gap between coastal and non-coastal areas has widened from 23% to 26% from 1997 to 2015.
Meanwhile, the government announced on Monday that it was providing £40m for coastal areas from the Coastal Communities Fund.
Having launched in 2012, it has so far provided £170m for 278 projects across the UK in five rounds of funding.
Some of the projects to have received funding include a new conference centre in Blackpool's Winter Gardens and improvements to Southport Pier.
Coastal Communities Minister Jake Berry said: "From the world-renowned Blackpool illuminations to Brighton's i360, our coastal towns and cities have a lot to offer all year round.
"This year is already looking like another record year for staycations and our latest round of funding will help attract even more visitors to the great British coast so that our coastal communities can thrive."