In the same week it lost the Unilever audit, PwC's relationship with Marks & Spencer has also come to an end with the news that the high street giant is appointing Deloitte as it statutory auditor.

PwC began auditing M&S in 1926, when the company was first listed on the Stock Exchange. In its 2013 annual report the retailer stated that its audit committee would put the audit out to tender in the coming year as 'recognises that length of tenure of auditors has been a topic of much debate'. The audit committee noted the UK Governance Code's requirement for the external audit contract be put out to tender at least every ten years.

Following completion of the audit of the accounts for the year ending 29 March 2014, Deloitte will be appointed as M&S's statutory auditor, subject to approval by shareholders at the AGM.

Andy Halford, chairman of the M&S Audit Committee, said: 'We thank PricewaterhouseCoopers for their significant contribution as M&S's auditors. We look forward to working with Deloitte going forward.'

M&S paid a total of £3.1m to PwC in the last financial year, of which £2m was for auditing the company and its subsidiaries. PwC was paid an additional 1.1m for tax compliance and tax advisory work, as well as other non-audit services.

In the annual report, the audit committee said the non audit fees were higher than in previous year. This was large because of two significant projects - one HR-related and the other to advise in the development of integrated controls framework to document the processes and controls across M&S' core business activities. The report states 'the Committee is very mindful that these were exceptional items and aim to maintain non audit fees at a lower level going forward'.

A spokesman for PwC said: 'Competition in the audit market is fierce and we do expect to see more companies switch auditor in response to regulatory change. We continue to retain and win audit clients, as we have done recently with companies such as HSBC, Hargreaves Lansdown and Ladbrokes.'