The party will also help "real” first-time buyers onto the property with a new mortgage guarantee scheme, the Labour leader told his annual conference in Liverpool.
As millions nervously await expected increases in the Bank of England base rate. Sir Keir said that under the Conservatives “the dream of owning your own home is slipping away for too many”.
He also accused the party of inflating demand without increasing supply, meaning “house prices will only rise. And homes become less affordable for working people”.
"So we will set a new target - 70% home ownership and we will meet it with a new set of political choices. A Labour set of political choices," he said.
He went on: "No more buy-to-let landlords or second homeowners getting in first. We will back working people’s aspiration. Help real first-time buyers onto the ladder with a new mortgage guarantee scheme. Reform planning so speculators can’t stop communities getting shovels in the ground.
"My message is this: if you are grafting every hour to buy your own home, Labour is on your side. Labour is the party of home ownership in Britain today."