The Oxford University Press has published the first in two volumes looking at all 700 surviving letters of Charles Wesley.

Wesley co-founded Methodism with his brother, John, and wrote scores of hymns, including the ever popular "Hark the Herald Angels Sing".

The first volume of The Letters of Charles Wesley focuses on his correspondence between 1727 and 1756. The second volume, to be published at a later date, will include letters up to the year of his death in 1788.

The collection is kept at the world-famous John Rylands Library and many of the letters featured in the two volumes are previously unpublished.

They offer Christians and researchers a fascinating insight into Wesley and the birth of Methodism, which was seen by many as a radical break from the organised religion of the day.

The two volumes are edited by Dr Gareth Lloyd of the University of Manchester's John Rylands Library and Professor Kenneth Newport of Liverpool Hope University.

"The early Methodist movement attracted the young, the rebellious and sometimes the downright eccentric, which is somewhat removed from the image of Methodism today," said Dr Lloyd.

Dr Lloyd is one of only a handful of people who can read the complex 18th century shorthand developed by John Byrom that some of the letters were written in.

"The publication of this collection will shine a light on a remarkable man living in one of the most significant periods in British history," he said.

"Charles Wesley was more than just a hymn writer. As co-founder of the Methodist movement, he established a family of Churches with an estimated 75 million members and one which is still growing in many countries.

"Wesley's genius as a preacher and religious leader contributed to the birth of the evangelical movement, probably the greatest success story of the modern Church.

"His life and ministry, even within Methodism, have received scant attention, so we are pleased that this collection will change that."

Professor Newport said: "These letters tell the fascinating story of a man who struggled against depression and crises of faith to create poetry that still has the power to move and inspire.

"They show Wesley as a devoted, but sometimes rather puzzled, family man who struggled at times to curb his young wife's extravagance.

"Wesley was an entertaining and forthright correspondent; his letters paint in vivid detail the everyday reality of 18th century life with its squalor, colour, laughter and tragedy.

"In short, the letters present a rich tapestry of public, private and religious life in Britain at a time of rapid economic and social change, seen through the eyes of a man who ministered to the urban poor and mixed with the social elite."