Labour's deputy leader admitted on Sunday it was understandable that workers felt "resentful" about benefits claimants that do not want a job as the party attempted to reposition itself on welfare.
Harriet Harman said it was "not surprising" that people were concerned about the system but claimed the government's failure to install a proper work programme was letting some people "off the hook".
The party is working on a policy proposals that would mean benefit payments to those out of work or on low incomes would vary according to their past contributions.
Harman told BBC 1's Andrew Marr Show: "The difficulty is for people who are in work, seeing their standard of living pressurised, understandably, they feel very resentful for people who are not working. For people who are looking for a job and can't find a work it's deeply frustrating and then of course the small minority who don't want to work - well they are let off the hook by the fact there isn't a proper work programme."
Harman said the party was working up three principles on welfare ahead of the general election.
She added: "One, that work should pay, secondly, there should be obligation to take work and thirdly that there should be support through a contributory principle for people putting into the system as well as taking out."
It comes after days of bitter clashes as a raft of major Coalition tax and welfare reforms took effect, including a below inflation 1% cap on working-age benefits and tax credit rises for three years.
Around 660,000 social housing tenants deemed to have a spare room will lose an average £14 a week in what critics have dubbed a "bedroom tax", and trials are due to begin in four London boroughs of a £500-a-week cap on household benefits.
Labour former welfare minister Frank Field, once famously ordered to "think the unthinkable" and then sacked, told Murnaghan on Sky News voters could not believe how his party had let the amount people could claim in benefits reach such high levels.
He said: "The £500 cap in my constituency is a mega sum. When it first came out voters were actually in Birkenhead (saying) 'have you allowed this to go on for this long?'"
He added: "The idea that we have allowed a welfare state to pay out these sums without trying to put some element of responsibility back strikes them as mad so I hope we are going to be really tough on that caps, really tough on making it (so) you have to actually do certain things to get welfare and above all you have got to pay in to get it."
Treasury chief secretary Danny Alexander said Labour's plans on welfare showed they were "out of touch".
He told Murnaghan on Sky News: "I think it is extraordinary today that the Labour party has come forward with its proposals to increase the cost of the welfare system.
"From the shadow work and pensions secretary, who was the person who left a note for my predecessor saying there is no money left, to now come forward with ideas to spend even more money on the welfare system just shows how out of touch with reality the Labour party are."
An opinion poll for The Sun found six out of 10 voters believe benefits are too generous and 79% back the Government's plan to cap a family's benefit at £26,000 a year.
Prime Minister David Cameron defended the welfare shake-up claiming it was "putting fairness back at the heart of Britain".
Writing for The Sun, he suggested it was "crazy" that claimants could have a bigger income on benefits than work and warned the system was causing "resentment" across the country.
Cameron said the system had "lost its way" and had become a "lifestyle choice for some".
He wrote in The Sun: "It was designed to bring us together, but is causing resentment. I think the British people are about the most fair and generous people on the planet - but no one wants to work hard every day and see their hard-earned taxes being used to fund things they themselves cannot afford or keep generations dependent on welfare."So this month we are making some big changes. They are changes that have a simple principle at their heart: we are restoring the fairness that should lie at the very heart of our tax and welfare systems."