Improvements carried out to boost the sale price of properties could leave homeowners significantly worse off, according to research.

With falling house prices, the majority of improvements would cost more to carry out than they would increase the value of people's homes, according to high street bank Abbey.

The research found that changes previously thought to boost asking prices, such as building an extension or adding a new kitchen, would now leave homeowners nursing five figure losses if they put their property up for sale immediately after carrying them out.

Consumers who add an extension in a bid to get a higher sale price for their home are likely to be more than £20,000 worse off, as the additional space would boost their house price by about £13,568, but would cost more nearly £34,000 to carry out.

People would also be nearly £14,000 worse off if they installed a new kitchen or built a conservatory immediately before putting their home on the market.

Making their home more environmentally friendly, such as by adding solar panels, would leave consumers £11,472 worse off if they then sold there home, while they would be about £9,600 out of pocket if they carried out a basement or loft conversion.

The only home improvement that estate agents think homeowners would be able to recoup their outlay on is cosmetic changes, such as repainting and decorating.

They estimate that people who spend just £1,330 sprucing up their property could increase its sale price by more than £3,500, giving them a net gain of more than £2,000.

Nearly a third of estate agents said they had changed the advice they gave to homeowners about home improvements during the past 12 months, with many no longer suggesting new kitchens and bathrooms were a worthwhile investment.

Phil Cliff, director of Abbey Mortgages, said: "Our research shows that very few home improvements will actually add more value than they cost to implement at the moment, so it's important that people are making these improvements because they want to live in the end result and aren't doing them in order to add value alone."

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