Evils of neglect, looting and development are threatening rich heritage of Pugin's churches

When Irish families fleeing from the potato famine arrived in Leeds 150 years ago it was little short of a miracle that they were soon able to build their own Catholic church. After giving all the money they could, the immigrants only reached their goal when a mystery benefactor delivered a gift of a thousand gold coins.

Yesterday, the fruit of their effort was in need of further divine intervention. The colossal Mount St Mary's Church in Richmond Hill, Leeds, designed by Edward Welby Pugin and still known as "the famine church", has a leaking roof and deteriorating stonework. It is also undergoing a developer's structural survey, provoking fears that it may be demolished after the report is issued later this month.

The threat to the building presents new cause for concern to admirers of Pugin, who probably ranks as one of Britain's most neglected architects. The son of Augustus, who designed the Houses of Parliament's intricate façade and interior, E W Pugin picked up his father's mantle and left a fine ecclesiastical legacy before his death at the age of 41.

But that legacy is being whittled away. Five years ago, his monastery of St Francis in east Manchester, another large Catholic edifice, was about to be converted into flats when the World Monuments Fund (WMF) named it as one of the world's 100 most important endangered buildings. It has since found salvation through the Heritage Lottery Fund. But Pugin's beautiful St Mary's Star of the Sea church at Leith, near Edinburgh, has been given no such reprieve. And his redbrick church at the Abbey of Our Lady of Consolation, in Worcester, was put up for sale last year.

As his churches fall into dereliction, their artefacts are being looted. Missing statues from St Francis's ended up on Manchester market stalls before the council stepped in to preserve them. Statues crafted in France also went missing from Mount St Mary's after it was closed as a place of worship in 1989. The Mount St Mary's Trust has since located them and delivered Saints Theresa, Joseph and Thomas of Canterbury, among others, to the safe-keeping of one of its members.

Ecclesiastical looting is becoming a serious problem. Last year 3,600 artefacts were stolen from churches in Britain, with statues, fonts and whole altars vanishing. Just before Christmas, Wells Cathedral in Somerset lost a priceless alabaster relief of the Ascension, and the monks at Prinknash Abbey, Gloucestershire, found that a statue of the Madonna had been removed. Both dated from the 15th century.

Pat Gavan, custodian of the recovered Mount St Mary's saints and a worshipper at the church for almost 50 years, fears demolition is on the cards, despite the assertion of the Pugin Society – which inspected the church last July – that this is a fine example of Victorian Gothic architecture.

"There has been scheme after scheme, allocations of money and grants, but nothing has happened," said Mr Gavan, who claims to have won support from the Prince of Wales and earned a mention for the church's neglect in Parliament. "I long for the day when the roof will be repaired, the floor renovated and people tread there again," he said.

Yesterday, the developer which owns the building, Sanctuary Housing, said its demolition was not a foregone conclusion. "We have spent a lot of time trying to come up with a solution," said Steve Wood, the company's director of asset management. "But we cannot close the funding gap because the building is in such bad condition."