A campaign has been launched to save a medieval church and one of the oldest buildings in Birmingham from crumbling to the ground.

St Giles Church in Sheldon was built 700 years ago and is one of only three churches in the city created during the Middle Ages.

It has survived the Reformation and the English Civil War and is famed throughout the world for giving rise to the Church of England's missionary movement. But its sandstone tower is eroding at such an alarming rate that in a few years it is expected to be so unsafe the church will have to close.

A drive has now started to raise the #40,000 repair bill and save the historic building.

Rev Brian Camp, Rector of St Giles, said: "There are three mediaeval churches in Birmingham.

"One in Yardley, one in Kings Norton and the other is us. We make up three of the oldest buildings Birmingham.

"The church is made of sandstone. Throughout the centuries the face of it cracks. Rainwater gets in, it freezes and opens up more cracks and the face and stone will start falling away.

"Our surveyor thinks there are some large chunks high up which will mean it will become dangerous to walk close to the church.

"It is not too distant when it will be too dangerous to use."

The church wants to raise #20,000 from the community and hopes to get match funding from bodies such as the Lottery Heritage Fund.

It fears if the work is not done soon, erosion will be so bad that it will cost up to #500,000 to repair.

Rev Camp said: "It is crucial that we are able to do the work in the next two to three years."

Among the church's more unusual features is a stained glass pentagonal window - a shape more usually associated with the occult - that was saved from destruction during the Reformation after locals bricked it over.

It was rediscovered in the 1860s - 200 years after it was covered up.

A "leper's window", described as a "squint in the wall" still exists where those suffering from the infectious disease were allowed to look in on services. The walls of the church also bear evidence of the Civil War, with bullet holes and scratch marks where Roundhead soldiers sharpened their pikes.

But perhaps of most significance is the legacy of the Rev Dr Thomas Bray, who was rector from 1690 to 1730.

His missionary work brought the Anglican Church to America and is credited with the formation of the Episcopal Church, currently embroiled in controversy over the ordination of gay bishops.

Rev Bray's work also resulted in the setting up of Anglican churches in southern Africa, India, Japan and China.

One of his missionaries - Charles Wesley - went on to found the Methodist Church.

"Within the history of the Church of England, St Giles is quite famous because it is where the missionary movement started 300 years ago," said Rev Camp.

"We get people from overseas coming to look at us because it is where their church started from. You can find bigger and prettier churches, but none with the same place in church history."

You can help with the fund-raising campaign at www.stgilessheldon.org