David Cameron will claim the Conservatives are the 'party of the working people' as Margaret Thatcher's right to buy housing scheme makes a return in the his manifesto launch today.

The Conservatives hope one of the most popular policies of their most successful peacetime leader will break the deadlock in one of the tightest election campaigns in a generation.

In an offer the Tories hope will win over Labour voters, Mr Cameron will promise that the Right to Buy scheme will be extended to 1.3 million families, giving them the chance to buy their home at a discount.

The Conservatives will claim it will be paid for by requiring councils to sell off the most expensive housing when it falls vacant, raising £4.5bn per year, with some of this money used for at least a one-for-one replacement. Mr Cameron will also claim that 400,000 more new homes will be built through a £1bn fund to unlock brownfield land.

The manifesto launch will come after a weekend when the Conservatives announced that they would find the £8bn which health experts claim the NHS needs, but were unable to spell out exactly where from.

The prime minister will say: 'At the heart of this manifesto is a simple proposition. We are the party of working people, offering you security at every stage of your life.

'If you're a young person looking for training, if you're looking for a decent job, if you want to buy your own home, if you're raising a family and need help with childcare, if you fall ill and need to rely on our NHS, if you are reaching retirement and want real security, we are there for you – offering security at every stage of your life.'

He will conclude: 'My message to Britain is this: we have come this far together. Let's not waste the past five years. Now is not a time to put it all at risk, but to build on the progress we have made. We are the party of working people. So if you want a more secure Britain, if you want a brighter future for your family, and for you then together let's build on what we've done – and see this through.'

The Right to Buy scheme allows tenants to buy their home at a discount. Until now the right has only been available to tenants in local authority properties and some former local authority properties. The Tories will claim that by extending the Right to Buy to housing association tenants in England up to 1.3 million more families get the chance to own their own their own home.

Homes sold to tenants will be replaced on a one-for-one basis.

Local authorities will be able to bid for money from the Brownfield Regeneration Fund to help them clean up derelict or contaminated land, and provide infrastructure to open up inaccessible brownfield sites.

The Tories claim the fund will unlock the construction of 400,000 additional homes over five years.