Housing minister Grant Shapps has revealed that some 50,000 plots have already been identified to build extra affordable homes.
Speaking at a fringe session at the Tory party conference organised by the Home Builders Federation and National House Building Council, he accepted the country faced a housing crisis but said the Government's plan to release land for housing were well advanced.
Last Sunday, David Cameroon estimated that 100,000 homes could be built on Government land, if released on a build now and pay later basis.
The Government has told all its departments to identify land that can be sold and the housing minister confirmed "space for 50,000 of the 100,000 homes has already been identified".
Shapps also defended measures to revitalise right-to-buy with bigger discounts.
Some housing association critics have warned that this plan could see the affordable housing stock eroded even further.
Karen Armitage, chief executive of Stafford and Rural Homes, said: "How a new house will be provided for every house sold through right-to-buy is unclear as obviously one cannot build a house in the same place or indeed at the same time as one that is to be sold."
The housing minister pledged that all proceeds from the sales will be directly reinvested in a further 100,000 new affordable homes.
At a meeting he said: "People have looked at this and quite rightly have been sceptical.
"But on this occasion this is going to stack up and the reason we know this for sure is that the affordable rent programme has already been an enormous success."
He reiterated that the affordable housing programme was on course to deliver 170,000 homes by 2015, ahead of the 150,000 first targeted.
With such pent-up demand the Government said it could fund a second wave of affordable homes using right-to-buy receipts.
Full details of the two measures to build an extra 200,000 homes will be released in the autumn.
Meanwhile, London Mayor Boris Johnson said London was on track to build a record number of affordable homes.
Speaking to the main conference, he said: "We are on target to build a record 50,000 affordable homes over four years and we will do even more over the next four.
"But we are also insisting on homes that are big enough for families and with rooms big enough for human beings rather than hobbits."
