An extension in taxpayer support for the property sector helped Britain's biggest house building firms add to share gains which have in some cases seen them double in value since the start of last year.

The four biggest listed companies have increased in market value by 81%, or £7.2 billion, over the period, which saw the Government introduce the Help to Buy scheme to kick start the sector.

Chancellor George Osborne will now extend an equity loan part of the initiative - which had been due to end in 2016 - until the end of the decade.

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It will mean another £6 billion invested to help an estimated 120,000 more households purchase a new-build home.

A separate element of Help to Buy introduced last year offers lenders £12 billion of mortgage guarantees to lure them back into making high loan-to-value ratio advances of up to 95% of the value of homes.

The latest announcement saw FTSE 100 listed builder Persimmon climb nearly 7% as traders digested its implications. Its value has already surged by about £2 billion, or 77%, to £4.3 billion, since the start of 2013.

Barratt, listed on the FTSE 250 Index, rose 3% - with its market capitalisation having gone up by 105%, or £2.1 billion, since the start of last year, to nearly £4.2 billion.

Taylor Wimpey climbed 4%. Its value has risen by 84%, or £1.8 billion to £3.9 billion, over the period. Berkeley, which lifted 2%, has grown in value by £1.3 billion, or 54%, since the start of last year, to reach £3.7 billion.

House builders' shares have been steadily climbing over the past year or so, aided by improvements in the overall economy and a property market which has been buoyed by Government support.