LONDON (Reuters) -- Four out of five British adults pay far more tax than they should because they either fail to claim rebates or they don't plan ahead, financial advisers said on Friday.

IFA Promotion (IFAP), which represents 9,000 independent financial advice firms, said 82 percent of adults failed to make the most of tax-efficient systems or allowances available to them -- apathy that would cost them around 7.6 billion pounds in 2006 alone.

"Tax is no-one's friend, so why pay more than you need to?" said IFAP chief executive David Elms.

"Whether through apathy or confusion, the failure to claim tax credits is just one way we're gifting unnecessary and vast sums of money to the taxman each year."

Elms said the biggest area of waste was in tax credits.

The government has set aside 13.3 billion pounds to pay for tax credits in 2006 but Elms said around 2.9 billion of that would go unclaimed unless more people applied for the pension credits, child tax credits and working family tax credits to which they were entitled.

The Treasury said on Thursday that 79 percent of families who were entitled to Child Tax Credit had claimed it and take-up was highest among low-income families.

"Tax credits are reaching more families than any previous system of financial support, with nearly 20 million people benefiting from them," said Paymaster General Dawn Primarolo in a statement.

Britons also paid more tax than was necessary by failing to plan properly.

Each year, around 1.3 billion pounds is paid in inheritance tax, which could be avoided in the most part by individuals taking time to write a will, complete a discretionary will trust or write their life insurance policies in trust.

Robert Guy, a financial consultant with London based Timothy James and Partners said paying too much tax was all too often the curse of the employed.

"For the self-employed, it (getting financial advice) is a natural extension of what they're doing. They are happy to pay people to help make their arrangements more efficient.

"Employed people don't necessarily see things that way, either because they think their arrangements are simpler or because they view it (advice) as a cost not a financial saving."

Guy said there was a huge amount of money being wasted and that the gulf between the haves and have-nots in terms of making every penny count was enormous, and widening.

The BBC's Money Program, broadcast on Thursday, said multimillionaires, such as fashion tycoon Philip Green, did the most to avoid paying tax.

The program said such tax avoidance by the super-savvy super rich cost the government an estimated 10 billion pounds each year.

The government established a special Anti-Avoidance Group in April 2005 with more than 100 members of staff. It aims to counteract methods and "payment in kind" schemes that planners who specialize in tax avoidance use to reduce their clients' tax bills.