One in 25 local areas of the UK saw their population fall over the last decade, new figures suggest.
The areas include Barrow-in-Furness and Copeland in Cumbria, Ceredigion in Wales and Inverclyde in Scotland, which saw the biggest percentage drop anywhere in the country.
By contrast, some parts of London are estimated to have seen population growth of more than 20% while places such as Coventry, Corby and Dartford all saw increases of around a fifth.
The figures have been published by the Office for National Statistics (ONS) as part of the annual population estimates for the UK.
They suggest that 17 out of 379 local authority areas, or 4%, are likely to have seen a decrease in population from mid-2010 to mid-2020, according to analysis by the PA news agency.
Inverclyde tops the list, with an estimated drop of 5.5% from 81,510 in 2010 to 77,060 in 2020.
Na h-Eileanan Siar, or the Western Isles, saw the second largest fall, down 4.0% from 27,600 to 26,500.
Barrow-in-Furness and Copeland are next, with decreases of 3.9% and 3.7% respectively.
A common factor to most of the local areas of England to see a fall in population is the seaside: Barrow-in-Furness, Copeland, Blackpool (down 3.1%) and Scarborough (down 0.3%) are all by the coast.
The one landlocked area of England where the population fell was the London borough of Kensington & Chelsea (down 2.2%).
All other areas of London are estimated to have seen their population rise from mid-2010 to mid-2020, with the City of London (up 49.1%), Tower Hamlets (33.6%), Camden (30.2%) and Westminster (24.2%) having the highest increases.
Outside London, the areas with the biggest rises are Coventry (up 21.7%), Corby (21.5%), Tewkesbury (18.5%) and Dartford (18.4%).
The highest increase in Scotland was for Midlothian (up 13.1%), for Northern Ireland it was Armagh City, Banbridge & Craigavon (9.6%), while for Wales it was Cardiff (8.1%).
The ONS said the estimates should be treated with caution, as the regular collection of statistics that are used for modelling population size has been disrupted by the coronavirus pandemic.
It is also nearly 10 years since the results of the 2011 Census, which the ONS has used as a starting point for estimating population figures during the past decade, adjusting each year for births, deaths, internal and international migration.
The first results from the 2021 Census are due to be published in March next year, and these will give the most accurate picture of how the population has changed.
The total population of the UK is estimated to have grown from 62.8 million in mid-2010 to 67.1 million in mid-2020 – a rise of 7%.
Here are the 17 local authority areas where the estimated population fell between mid-2010 and mid-2020.
The list reads: name of area; estimated population mid-2010; estimated population mid-2020; percentage change.
Inverclyde: 81,510; 77,060; down 5.5%
Na h-Eileanan Siar: 27,600; 26,500; down 4.0%
Barrow-in-Furness: 69,429; 66,726; down 3.9%
Copeland: 70,629; 68,041; down 3.7%
Argyll & Bute: 88,620; 85,430; down 3.6%
Ceredigion: 75,217; 72,895; down 3.1%
Blackpool: 142,753, 138,381; down 3.1%
West Dunbartonshire: 90,800; 88,340; down 2.7%
North Ayrshire: 137,800, 134,250; down 2.6%
Kensington & Chelsea: 160,463; 156,864, down 2.2%
Dumfries and Galloway: 151,100; 148,290, down 1.9%
Shetland Islands: 23,060; 22,870; down 0.8%
East Ayrshire: 122,410; 121,600; down 0.7%
South Ayrshire: 112,600; 112,140; down 0.4%
Scarborough: 109,014; 108,737; down 0.3%
Isles of Scilly 2,228; 2,226; down 0.1%
Clackmannanshire: 51,330; 51,290; down 0.1%