“I don’t accept that it will not affect sales. I have been in the industry 35 years and I can think of a huge number of impulse sales where people have dipped their toe in the market, found the temperature to their liking and decided to sell.

“We are particularly worried about first-time sellers who may not have much in the way of savings and may decide it’s not worth the risk.”

The packs provide basic information about a home including local authority searches and details about whether the property is environmentally friendly.

Ministers claim the packs will speed up the buying process and lead to savings of £80million a year But in a further blow, the study shows that searches will have to be renewed if a property has not sold within six months.

It means a quarter of all sellers, about 500,000 a year, will have to renew ­information in their packs at least once, at a cost of up to £270 a time. The assessment also shows the Government will have to give councils £2.2million a year to employ an army of inspectors to police the scheme.

Figures released this week showed a record number of homes were put on the market last month in a bid to beat the packs’ original June 1 deadline.

Last year the Government had to abandon plans to include a property survey in the pack after mortgage lenders warned they would not accept it as proof of a home’s condition. Ministers last month had to delay the scheme because of legal challenges and a shortage of inspectors.

Communities Secretary Ruth Kelly said the scheme would be delayed by two months and would initially apply only to homes with four bedrooms or more, leading observers to believe it would be abandoned in the summer. However, the Department for Communities and Local Government says the packs will be applied to all properties this year and claims the cost is “unlikely to deter those who are serious about selling”.