The Secretary of State for Work and Pensions says the new benefits system will "adapt and change" to ensure it is fit for purpose.
Ms McVey repeatedly pointed to figures that the Conservative government has got more than 3,000,000 people back into work since 2010, with the aim of Universal Credit to make the employed better off.
"Well it isn't indifference, it really is about supporting people into work - we're getting 1000 more people into work every day and, at the same time, we've also got to listen to the most vulnerable," Ms McVey told ITV News.
Universal Credit, which is being rolled out gradually, replaces six existing benefits with a single payment – but critics have argued the programme, which has been subject to several delays, is flawed.
The Public Accounts Committee (PAC )said the DWP has persistently dismissed evidence Universal Credit is causing hardship for claimants and additional burdens for local organisations and “refuses to measure what it does not want to see”.
Asked about the working families negatively impacted by the rollout of Universal Credit, Ms McVey said: "There shouldn't be any families suffering, we don't want that."
PAC said the department’s “fortress mentality” is failing claimants who are struggling to adapt and being left worse off.
"What we know is we've got more than 3,000,000 more people into work," Ms Mcvey said. "What we know is we're helping helping the most vulnerable, we're giving people the help and support they need through UC.
"And what I will say, too, is where we need to adapt and change, and where we have to make the system work even better that is exactly what we will do.
"We will work as a government, we will work as a team because our whole aim in life is to support these people."
PAC said: “The introduction of Universal Credit is causing unacceptable hardship and difficulties for many of the claimants it was designed to help.”
A “department in denial” cannot learn from mistakes and the culture needs to change, the PAC said.
One claimant left worse off by Universal Credit is Justine Pyatt, a single mother who was refused her childcare benefits after putting in her claim a day late, resulting in her going into debt.
Due to her being worse off on Universal Credit, a system she claims those employed to run it don't even understand, she has been forced to leave her job to become a stay-at-home mum.
The mother-of-two told ITV News: "It's hard enough to go to work as a single parent of a one-year-old and an eight-year-old, as it is, let alone try to work out a system that even the people that work there don't even understand how the system works.
"Yet the expect you to understand and they've failed me, they've completely failed me and consequently, I've lost my job."
A DWP spokesperson said: "We will carefully consider the findings in the report - a number of which we are already working on. For example, we have recently begun a new partnership with Citizens Advice to deliver better support to the most vulnerable, and are working with stakeholders to ensure the Managed Migration process for people moving onto Universal Credit works smoothly.
"So far this year we have already announced several improvements to Universal Credit, such as plans to reinstate housing benefit for vulnerable 18-21 year olds, making direct payments to landlords, offering 100% advances and providing an additional 2 weeks of housing benefit for claimants."