The Conservatives have accused the government of a "U-turn" over its plans to delay the introduction of part of its flagship house sale packs.
Tory Michael Gove says ministers should scrap the whole scheme
Housing Minister Yvette Cooper says the survey element of the packs needed further testing and will not come into force in June 2007 as planned.
There are also concerns there will not be enough inspectors to cope with demands for home condition reports.
Michael Gove, for the Tories, said the plans are now "a complete shambles".
His party has urged the government to scrap the packs, which it says could cost homeowners up to £1,000 each.
The scheme is due to start in England and Wales in June 2007. Ministers insist it will speed up sales and make the process cheaper.
The new law will require sellers to assemble, at their own cost, a pack including title deeds, local authority searches, answers to standard questions and energy performance certificates - all of which will be given to any potential buyer.
The aim is to knock weeks off the normal house-buying process, reduce the scope for gazumping and to make sure fewer deals fall through.
But Ms Cooper said the introduction of the survey, or home condition report (HCR) element of the pack, would be postponed - following dry run tests on 14,000 home information packs with searches.
"We have concluded that there would be significant risks and potential disadvantages to consumers from a mandatory 'big bang' introduction of full home condition reports on 1 June 2007," she said.
Further testing was needed to make sure the HCRs delivered "the assumed benefits for consumers and that the operating systems that support them work smoothly.
"Design work on the dry run has made it clear that this cannot be completed in time for the results to be taken into account by 1 June," she said.
The Council of Mortgage Lenders say some lenders may not be "fully geared up" to use HCRs until 2008-9, meaning they would continue to seek separate mortgage valuation surveys.
Mr Gove, the Conservative's shadow housing minister, said: "The government's ongoing plans for home information packs are now a complete shambles.
"The government should abandon the whole scheme and consult afresh, rather than move ahead with a vanity project to save ministers' faces."
Andrew Stunell, the Liberal Democrats local government spokesman, said he was pleased ministers had responded to calls to pilot the packs.
"There can now be a realistic assessment of how they will work and what snags there may be," he said.
Trading standards warning
But he added: "Those pilots must be thorough and not simply become another tool of the spin doctors."
Charles Smailes, president of the National Association of Estate Agents (NAEA), "The announcement today is something of a U-turn by the government on legislation it has been working on for over five years.
"It calls into question the effectiveness of a home information pack when the documentation included is now largely available online.
"The legislation would seem unnecessary and does not cover the important reasons why home sales and purchase transactions fall through."
Lacors - the local authorities' co-ordinator for regulatory services - warned that local trading standards officers did not have sufficient powers to ensure people selling their homes had compiled a pack.
Mike Ockenden, director general of the Association of Home Information Pack Providers, said he believed that "there will be consumer demand for the HCR and it will become mandatory".
The government says the packs will cost about £650 for each seller to put together, but save buyers £1m a day, which they currently waste in aborted transactions.