The trustees of Canterbury Cathedral have admitted that £50m is needed to rescue the 'crumbling' building - regarded as the "mother church" of the Anglican Communion.

A list of problems plague the building, according to surveyors, who have told of masonry crashing down from parts of the building, leaking roofs and stone and Purbeck marble pillars held together with "bits of string" to keep them safe, according to a report by The Times.

Now cathedral trustees have drawn up a £30m strategy in a bid to reverse the combination of old age and modern pollution that the cathedral's trustees say are causing serious damage.

At least £7.5 million is needed to fund the vast amounts of lead needed to replace the roof of the Early English Gothic building although the conservation work on the building's crumbling Caen stone will be even costlier.

The trustees added that the consequences would be "potentially disastrous" for the 900-year-old building if urgent action were not taken. The target date for completion of the rejuvenation project is 2016.

Referring to the cathedral as "the mother church of the Anglican Communion", the Archbishop of Canterbury, Dr Rowan Williams, said: "Generations have played their part in creating and preserving this magnificent building. It is time for us to do our bit."

The cathedral receives no government aid or cash from the Church Commissioners to help with maintenance but instead relies on the £6.6 million it generates in income from the more than one million people who visit the cathedral each year.

Even among the visitors, many do not pay the full entrance charge of £6 because they live in the diocese or worship there. Further reductions are offered to parties and under-18s, senior citizens and students, and there are discounts for pre-booking.

Conservation costs include a further £6.5 million required for internal repairs, coloured-glass restoration, new lighting and better facilities for people with disabilities.

In addition, the organ needs a £4 million refurbishment and £2 million will be need to modernise the choir house, The Times reports. A further £11 million is to be spent on visitor facilities, education and the preservation of artefacts, including a "signature", or two crosses, of the illiterate William the Conqueror and another document signed by King Henry II relating his penance for the murder in 1170 of Thomas à Becket. The choristers also need a £3 million endowment.

Lord Hattersley, the politician and journalist, who is an atheist, said: "Canterbury Cathedral is important to people of all faiths, and none. Canterbury is not just a building. It is England in stone and glass."