Opening hours and access to estates, works of art and antiques, which are also made available to the public to avoid duties, have not been sufficiently advertised. As a result, the Commons Public Accounts Committee said in a report into the collection of inheritance tax, 'not enough has been done to ensure that the public has been able to benefit fully from the very large sums of tax forgone'.
The committee was also critical of the way inheritance tax was self-assessed. 'In one case, the executor had sworn an oath that the estate was worth pounds 70,000 when its true value was pounds 870,000 and tax of pounds 426,000 was payable.' In that case, the Revenue's response was to send a letter of admonishment to the executors' solicitors.
Inheritance tax is levied at 40 per cent on a deceased's estate over pounds 150,000. But because of various reliefs and exemptions, while 650,000 people died in Britain last year, fewer than 25,000 estates paid any inheritance tax.
Staff shortages have led to the processing of 10,000 cases without detailed examination and the writing-off of an estimated pounds 20m a year. Owners of property deemed to be part of the national heritage are granted 'conditional exemption' from paying hundreds of millions of pounds in tax - provided they give undertakings about maintaining the property and granting public access.
Last year pounds 41m in duties were avoided by donations of works of art and furniture and pounds 2m from donations of land. But a Revenue official acknowledged the total fluctuates wildly from year to year. 'It just needs one or two very big cases for the figure to go up.' Over the last decade, about pounds 1bn worth of exemptions had been granted.
Works of art and antiques are entered on a register kept by the Victoria and Albert Museum in London. That list contains 9,000 items - the existence of which and the fact they are available for loan to museums and galleries, MPs said, 'may not be widely known'.
Deals with the Revenue are confidential, but MPs were supplied with examples where exemptions had been given. These included: a Turner painting, valued at pounds 12,000 in 1983, which may be viewed by appointment; a Rubens, worth pounds 150,000 in 1987, on loan to a provincial museum; a house and castle in the North of England, which was valued at pounds 750,000 in 1978 and is required to be open to the public for 60 days a year; a house in eastern England which was open for 30 days in 1993.
The only example named by the Revenue was Chatsworth, seat of the Duke of Devonshire. In 1978, about 12,000 acres there and a further 6,000 acres near Buxton, in Derbyshire, were exempted from inheritance tax. 'The public has access to over 128 miles of footpaths . . . and 800 acres of land.'
But the amount of tax saved at Chatsworth was not specified - something that was deplored by Alan Williams, Labour MP for Swansea West and a member of the Public Accounts Committee. He attacked the insistence on secrecy, claiming English Heritage and the Countryside Commission, the quangos involved in deciding if the property is part of the national heritage, 'cannot ask if the deal is good value for money, in terms of the tax forgone, because the financial information is confidential'.
He described the exemption system as 'a greasy pole for serious wealth to pass tax-free from one generation to another'.