One in five jobs across the UK pays less than the living wage, according to analysis by the Trades Union Congress (TUC).
Its report, which analysed official figures from the House of Commons Library, has been published to coincide with the 15th anniversary of the introduction of the minimum wage and the second week of its campaign, Fair Pay Fortnight.
The living wage is currently set at £8.80 per hour in London and £7.65 per hour across the rest of the UK.
The analysis found that, in some constituencies, nearly half of workers earn less than this.
Kingswood near Bristol tops the list of living wage black spots with 48% of people working there earning less than the living wage, followed by Chingford and Woodford Green in north east London (where 43.4% of jobs pay less than the living wage), Harrow West in north west London (42.4%) and Sefton Central on Merseyside (40.4%).
Other areas of the UK where employees earn less than the living wage include Dwyfor Meirionnydd in North Wales (39.9%), Rhondda in South Wales (39.7%), Blackpool South (39.3%), West Lancashire (38.2%), Bexleyheath and Crayford in south east London (38.2%) and Wells in Somerset (38.1%).
More than half of women working in two constituencies, Kingswood (56.1%) and Bexleyheath and Crayford (51.3%), are paid less than the living wage.
Around half of women working in Heywood and Middleton in the north west (49.7%), East Yorkshire (48.6%) and Cleethorpes (48.4%) earn less than the living wage.
However, in other parts of the UK, as few as 5% of employees are paid less than the living wage.
For instance, just 5.6% of people working in Poplar and Limehouse in east London, 5.8% of people working in Runnymede and Weybridge in Surrey, 7.3% of people working in South Cambridgeshire and 7.3% in Islington South and Finsbury in north London earn less than the living wage.
Frances O’Grady (pictured), general secretary of the TUC, said: “Extending the living wage is a vital way of tackling the growing problem of in-work poverty across Britain.
“Working families are experiencing the biggest pressure on their living standards since Victorian times. Pay has been squeezed at all levels below the boardroom and it’s costing our economy dear.
“The number of living wage employers is growing rapidly and unions are playing their part in encouraging more employers to sign up and pay it, but government must show equal initiative.
“We need to see a far greater commitment to pay the living wage from government and employers, and modern wages councils which could set higher minimum rates in industries where employers can afford to pay their staff more.
“During Fair Pay Fortnight we’re asking workers to back our call to MPs to get all political parties to put decent pay at the top of their agendas in the run up to the election.”