Work and Pensions Secretary Iain Duncan Smith has accused Labour of using generous welfare payments to "buy votes" as he promised the vulnerable will be treated with the "utmost kindness" when £12bn is cut from the social security budget.
The Conservative Cabinet minister said Labour "dramatically" increased top-up welfare payments to low-paid workers, or tax credits, in the run up to general elections.
His blast at the Opposition came as Mr Duncan Smith said people with disabilities would be afforded the "utmost kindness and utmost support" when the Government makes further welfare savings.
However, he ducked calls to give a "cast-iron" guarantee that the disabled would be exempt from cuts, claiming only Labour is fixated "scaring people".
The exchange in the House of Commons followed David Cameron giving a major speech on welfare, promising an end to the "ridiculous merry-go-round" of taxing low earners then handing them money back in benefits.
Later, during Work and Pensions Questions in the Commons, Mr Duncan Smith condemned Labour for overseeing a 60 per cent increase in the social security bill during their 13 years in power.
He went on: "We have had a lot of Labour people going on about tax credits.
"Just before every election the Labour government increases tax credit spending dramatically - in 2001 by 60 per cent, just before 2005 by 7.2 per cent and just before the 2010 election by 14.4 per cent and 8.5 per cent.
"The truth is the Labour Government has always used benefits as a way to buy votes."
Mr Duncan Smith was repeatedly questioned by Labour MPs about immunity from the latest austerity drive for the most vulnerable.
Veteran MP David Winnick said the Government had launched a "campaign of harassment" against the disabled.
But Mr Duncan Smith told Parliament: "It is our purpose to protect the most vulnerable. It has been from the beginning and it will continue to be so.
"There is no reason why people should be fearful. I do hope Labour MPs don't start to whip that up.
"Our purpose is to reform welfare to get people back to work and ensure those who cannot and cannot manage and have disabilities are treated with the utmost kindness and utmost support."