The UK Labour party has warned that thousands of computer systems used by the public sector will be open to cyber-attacks when Microsoft ends free PC support in April 2014.
The systems used by HMRC and the NHS in England and Scotland will remain powered by Windows XP OS after Microsoft ends its support lifeline that protects government systems from cyber attacks.
Shadow Cabinet Office Minister Jonathan Ashworth told the Guardian: "Millions of families will be fearful that their private health and tax information could be stolen as a result of the government's failing computer protection programs.
"Ministers must urgently disclose how many people could be at risk and what action is being taken to protect people's personal details.
"The country will expect nothing less than clear answers and concerted action."
Neither of the agencies will fund protection, while consumers will still be allowed to access the internet from their vulnerable Windows XP devices and using Internet Explorer 6 browser, according to the Labour party.
An HMRC spokesperson said: "HMRC takes security extremely seriously and has many controls in place to guard against online threats. HMRC is already upgrading our IT software and our systems will remain secure whilst this is happening."