The second phase of the scheme was originally set to be launched in January 2014 however the coalition has now taken the decision to launch it some three months early.
Applications will now be allowed from early October, although lenders will not be able to buy guarantees for the mortgages they offer until 1 January 2014.
The second phase will help people purchase a property with just a 5% deposit with the government guaranteeing the next 15% of the loan for seven years to reduce banks risks of losses.
HM Treasury confirmed that several high street banks will be offering the new Help to Buy mortgages to customers after Cameron told The Andrew Marr show that RBS, Natwest and Halifax will all be launching 95% mortgages.
RBS confirmed it was aiming to support some 25,500 first-time and next time buyers through the scheme.
Ross McEwan, chief executive of UK retail at RBS, said: “We’re committed to helping people get on with their lives, to buy their first home, move to a bigger house as their family grows.
“We fully support the Help to Buy mortgage guarantee scheme and we welcome news that it will be launched soon.”
The early introduction of Help to Buy is just one of several measures - including a tax break for married couples and extended cancer drug funding - being announced by the Conservatives at their annual conference in Manchester.
