Norwich & Peterborough Building Society (N&P) is to set aside £57 million in its accounts as provision over the issue of mis-sold Keydata structured products.

The issue has plagued the building society for a number of years and will now write to investors inviting investors to apply for ex-gratia payments in exchange for the transfer of investment rights relating to the products.

Chairman Gordon Horsfield said the society was deeply concerned for customers affected by the mis-selling and was 'very sorry for the hardship and anxiety' it had caused.

Keydata products were bought by 3,200 of the society's customers between 2005 and 2009, worth around £53.9 million, before the structured product provider was placed in administration

The society has already agreed the basis of calculation of payments  with the Financial Services Authority and the Financial Services Compensation Scheme.

Jeff Pritchard, finance and risk director, said,  'As these results demonstrate, N&P has a good underlying business which continues to offer attractive savings and mortgages to its customers.

'The Keydata provision is a one-off event which the society has the resources to cope with.'

The society had recommended fixed income and growth products provided by Keydata Investment Services backed by assets, issued by Luxembourg-based SLS Capital and Lifemark.

SLS was put into liquidation in 2009 with income payments stopping in July of that year, Lifemark was put into provisional administration in 2009 with payments suspended in January 2010.

N&P made a loss of £48.9 million for 2010. The building society said operating profit would have been £5.1 million without the Keydata provision and that it remained within capital requirements.

Chief executive Matthew Bullock is to leave the Norwich & Peterborough at the end of March, while the society announced that marketing and sales director Mike Hounsell had resigned and left at the end of February.