The loss of personal data by HM Revenue and Customs is symptomatic of the Labour government's "bureaucratic over-reach", David Cameron has warned.
David Cameron has vowed to fight "outdated ideology"
The Tory leader branded the government "enemies of freedom" driven by "outdated ideology" in a speech in the Czech capital, Prague.
He was addressing a conference of the ruling Civic Democratic Party (ODS).
Tories and the ODS plan to form a new European Parliament grouping after European elections in 2009.
Mr Cameron hailed the centre-right party's record of cutting taxes, of economic reform and fighting EU regulation.
He told activists that both the ODS and Tories were battling "a renewed assault on our liberty", and said: "Today, in this continent and around the world, history is on our side."
Mr Cameron accused ministers of allowing the state to "creep further and further into the lives of British people" because of old-fashioned notions that officialdom knows best.
"They do not mean to harm us. In fact, they mean to help us. But their ideas are out of date, their methods have failed and their advance must be derailed," he argued.
Mr Cameron continued: "This week we saw a shocking consequence of this bureaucratic over-reach: a scandal where the Government has lost the names, addresses and bank details of almost every family in the country."
David Cameron and the Czech PM plan to join forces in Europe
The proposed national identity card register would compound the problem, he predicted.
The Tory leader also turned his fire on bureaucratic over-reach in the EU, which he said was driven by "the desire for harmonisation and homogenisation - on tax, on regulation, on so many aspects of public and private life".
And he added: "It is the last gasp of an outdated ideology, a philosophy that has no place in our new world of freedom, a world which demands that we fight this bureaucratic over-reach and lead Europe into the hope and potential of a new, post-bureaucratic age."
Mr Cameron also held private talks with ODS leader and Czech Prime Minister Mirek Topolanek.
The ODS is the only other party to have signed up to his plan to create a new centre-right grouping in the European Parliament, the Movement for European Reform.
Tories and the ODS plan to leave the right-of-centre European People's Party.