Two elderly sisters fighting for the same rights as married and gay couples will make a last-ditch legal appeal for equal treatment today.

Joyce and Sybil Burden, born in 1918 and 1925 respectively, have lived together in Ogbourne all their lives.

They have willed their house to each other - but face crippling inheritance taxes because UK law only exempts property passed between spouses or civil partners.

The Burdens have already lost one case at the European Court of Human Rights in Strasbourg.

Now their lawyers are making a final appeal, arguing that the UK Civil Partnership Act of 2004 breaches the European Convention on Human Rights.

The Act gave gay and lesbian couples the same rights as married heterosexual couples. But the benefits, including passing property tax-free between partners, do not extend to co-habiting family members.

Joyce and Sybil are both worried that when one of them dies the surviving sister will have to sell the A£875,000 four-bedroom house and 30-acre farm to pay the 40% inheritance tax on its value - a burden not faced by married couples or civil partners.

Their concern is not recent - the spinsters have written to the Chancellor of the day before every Budget since 1976 seeking exemption from inheritance tax for family members.

Finally, in the wake of the 2004 Act which recognised gay and lesbian couples for inheritance tax purposes, they turned to the European Court of Human Rights, claiming the Act violated Human Rights Convention articles outlawing discrimination and guaranteeing the "protection of property".

Last year they lost the case by a 4-3 majority vote of the judges, and launched an appeal.

The appeal hearing, before a larger, 17-member panel of judges, will last a few hours - but the outcome of the final round in their battle is not expected until late this year or early next year.