Church leaders have urged Norfolk's rural parishes to keep their historic buildings open, despite fears that some could lock their doors to halt the 'growing menace' of metal thefts.

Home secretary Theresa May has announced a crackdown on the illegal trade in stolen metals, which will prohibit cash payments for scrap and significantly increase the fines for all offences under the Scrap Metal Dealers Act.

Those tighter legislative deterrents have been welcomed by MPs, landowners and the clergy following a spate of recent crimes, including the theft of a bronze 'corpus' of Christ from the Catholic church of St Joseph in Sheringham.

But it has also provoked a debate about the best way to safeguard the county's medieval treasures.

The general advice from the Diocese of Norwich – and from ecclesiastical insurers – is that a continual passage of worshippers and tourists actually makes open churches a less attractive target for thieves.

But one retired Norfolk priest said wardens in some isolated rural parishes were so fearful of losing valuables and antiquities, that they were considering locking their doors during the week.

Fr Peter Barnes-Clay was previously the rector of several remote north Norfolk parishes including Winterton and Weybourne, and is the former Rural Dean of Holt.

He said the financial concerns went beyond the simple loss of property, as lead-stripping could cause expensive damage to the fabric of the buildings and repeated thefts could cause insurance premiums to rise.

'A lot of country churches do lock – but we feel it's very important the church is kept open,' said Fr Barnes-Clay.

'We are all tied to the parish churches and their availability for daily prayer, so a locked church is a contradiction in terms. But sadly we live in times when a sense of the sacred has largely departed for a significant section of the population.

'I don't think this is officially going to affect the open churches policy directly and there are a lot of congregations who are equally determined to remain open. But it is of concern.

'Those with responsibilities for parish churches, whether the PCC (parochial church council) or the wardens, are very astute and they are not prepared to keep a church open to such a degree that the insurance rockets.

'The diocese has expressed a wish for churches to remain open, but we have to be realistic. They can cope with increased security during open churches week, but in the long term they cannot have someone on guard 24 hours a day, seven days a week.'

Archdeacon of Norwich, the Ven Jan McFarlane, said the security advice published by the Ecclesisatical insurance company was 'exactly the opposite' of locking the doors.

'They recommend churches should keep open so it can be used by the whole community,' she said. 'The incidents of thefts from open churches are actually lower, so it is not going to affect their insurance premiums at all.

'Some of my churches in the city remain closed because of vandalism, but in terms of thefts, an open church is broken into less than a closed one. The thieves will never know whether someone else is going to walk in on them.

'Obviously churches should put away anything of great value and replace silver and gold crosses and candlesticks with wooden ones during the week. But the church is safer open, that is the message.'

The home secretary's statement on Thursday said new legislation was 'the only sustainable, long-term solution to the growing menace of metal theft.'

The announcement was welcomed by Anne Sloman, chairman of the Church of England's Cathedral and Church Buildings Council – and a member of All Saints' Church in Sharrington, near Holt.

'This is excellent news,' she said. 'The church has campaigned for a long time for legislation to outlaw cash transactions for scrap metal. We are still suffering the theft of lead from 10 church roofs a day, and every weapon the government and the police can use to help us combat this crime is greatly to be welcomed.'

The Country Land and Business Association (CLA) East regional director Nicola Currie said: 'The high price of metals is the main factor in the flurry of recent thefts across the region.

'The CLA has been lobbying for better regulation of scrap merchants, particularly when it comes to cash payments for metal, which many see as the root of the problem.'

South West Norfolk MP Elizabeth Truss also supported the government's crackdown.

'It has a been a particular issue in South West Norfolk with Downham Market being one of the 'hot spots' for metal theft,' she said. 'Tougher legislation with significant fines will act as a deterrent to those who feel stealing scrap metal is an easy way to generate cash.'