Almost seven million adults of working age are struggling financially, finding it difficult to feed themselves and their families despite working full-time, it has been reported.
Around 3.6 million households say they are unable to cope on their income and have no assets or savings to fall back on, leaving them vulnerable if they face a sudden large expenditure, according to an Experian study for the Guardian.
The research by Experian Public Sector looked at households which fell outside the most deprived - people who were working but under high levels of finance-related stress, analysing their attitudes and behaviour.
Frank Field, the Labour MP for Birkenhead and former welfare minister who now advises the coalition on poverty, told the newspaper the findings were "a mega-indictment on the mantra of both political parties, that work is the route out of poverty".
Mr Field said: "What's shocking about this is that these are people who want to work and are working but who, despite putting their faith in the politicians' mantra, find themselves in another cul-de-sac. Recent welfare cuts and policy changes make it difficult to advise these people where they should turn to get out of it - it really is genuinely shocking."
The newspaper said the research showed that 2.2 million children live in families struggling financially despite one or both parents being in a job paying a low or middle-income. They included childless couples earning between £12,000 and £29,000 and couples with two children earning between £17,000 and £41,000.
A spokesman for the Department for Work and Pensions said: "For years the welfare state has not helped those people who are in work but on low incomes.
"The whole point of universal credit is that it will help make work pay and help those on lower incomes, topping up wages ensuring it is financially better to always be in work than on benefits.
"What is clear and this research shows, is that the existing system doesn't help those families who strive to do the right thing.
"This will change when our reforms come into effect. By sweeping away the complexities of the current benefit system, universal credit will be simpler and more straightforward for people to claim."