MANY Britons face a "nasty surprise" when planned changes to child benefit come into force next week, Labour has warned.

The Coalition Government claims households are well aware of the changes, which will result in more than one million people losing some or all of the hand-out.

Officials have written to 784,000 of the estimated 1.1 million households affected by the planned change and insist the message is "getting across". Yet this means more than 300,000 have not been contacted.

David Gauke, the Treasury minister, said: "So far we are getting a good response; slightly more people have opted out of child benefit than we had expected and that suggests the message is getting across."

He added: "We're trying to write to as many people as possible, but HM Revenue & Customs doesn't normally write to everybody every time there is a tax change that affects them."

Those affected can either opt out or pay a new tax to cover the cost of the payments. At present, some 183,000 people have chosen not to receive the pay-out.

"There could be a nasty surprise in store for thousands of parents if they are not aware of the changes and have to pay back thousands of pounds in child benefit at the end of the year," said Catherine McKinnell, the Shadow Treasury Minister.

MPs on Tuesday will debate a three-year 1% cap on annual increases.