In the face of a legal challenge from the Royal Institution of Chartered Surveyors (RICS) ministers bowed to pressure and pushed back the start date for mandatory sellers' packs from June 1 to August 1.

The controversial packs will also now be subject to a staggered roll-out and will only initially apply to sellers of houses with four or more bedrooms. The proposed delay and phasing in of the scheme failed to appease opponents of HIPs and was attacked by green groups as "bad news for the fight against climate change".

In a statement to the House of Commons, Ms Kelly said HIPs were to be delayed in light of the launch of a judicial review by RICS. A preliminary view from the Honourable Mr Justice Collins in relation to the case called for the dropping of Energy Performance Certificates (EPCs) - a crucial part of HIPs - if the launch date of June 1 was to be made.

Ms Kelly said introducing HIPs without EPCs would be neither practical nor acceptable and as such opted for a delay.

The Government also revealed on Tuesday that the number of certified energy assessors needed to meet the June 1 deadline had not been met. Previous estimates have shown that 2,000 fully trained and accredited assessors will be needed.

At present only 520 are ready for the launch of HIPs, although a further 1,000 have completed training and are awaiting accreditation. Packs will now see a phased introduction, with the scheme extended as and when sufficient energy assessors become ready.

At first only sellers of large houses - four bedrooms and above - will need to have a HIP, as they are deemed to be the most energy inefficient. In a further change to existing proposals, sellers will only need to have commissioned a pack before they put a property on the market, as opposed to waiting until they have a HIP in place.

The sellers' packs were conceived as a way of tackling the problem of transactions that collapse late in the day causing stress and financial loss to would-be buyers. HIPs will include up-front information about a house and an energy efficiency report.

Following Tuesday's announcement, Dave Timms, green homes campaigner at Friends of the Earth, said: "We are furious that the Royal Institution of Chartered Surveyors' legal challenge has forced the Government to delay the introduction of EPCs."