The Prime Minister was challenged over her plan to protect the value of inherited estates by imposing a cap on social care costs.
She said: "We are forward a proposal which means that people don't have to sell their house in their lifetime to pay for care.
"It means they can pass on savings to their children. And it means there will be that cap. But it's fair across the generations."
The PM also said previous social care plans protected wealthier pensioners but did nothing for those on modest incomes.
She told a studio audience: "The proposals I have put forward actually do that.
"They protect pensioners on modest incomes and crucially they ensure we have a long-term sustainable solution for social care."
Theresa May defended her proposed changes to social care Snap election 2017: The pictures politicians may not want you to see Sat, May 27, 2017
Protests, fights and daleks, it's all happening as the politicians hit the campaign trail for the snap election
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Jeremy Corbyn during a visit to Hackney Marshes Football Pitches, to highlight Labour's manifesto commitment to ensure 5% of the Premier League's television rights income is diverted to the grassroots game, during a General Election campaign
Don't listen to Corbyn's scare campaign
Foreign Secretary Boris Johnson tweeted: "Strong, clear and honest answer on social care from the PM.
"Don't listen to Corbyn's scare campaign #BattleForNumber10."
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Justice Secretary Liz Struss added: "Strong, honest answer from PM on social care. #BattleForNumber10."
She said she was determined to do the 'right thing' for the UK
Mrs May insisted she was determined to do the "right thing" for the UK, referring to her reputation as a "bloody difficult woman".
She said: "Doing what is the right thing by the country, sometimes you have to be difficult in order to do that.
"We need to have a government that is open about these things and is willing to find ways of addressing them."