Grant Thornton has been named as the new external auditor for the Takeover Panel.
PricewaterhouseCoopers had previously fulfilled the role and Grant Thornton partner Judith Newton described winning the job from the Big 4 firm as "impressive ".
The Takeover Panel contract means Grant Thornton is now the external auditor for three major regulatory bodies - the Financial Services Authority and Institute of Chartered Accountants in England and Wales being the other two.
Ms Newton suggested that was an indication that the Big 4 can no longer expect to monopolise the most prestigious public sector
audit jobs.
"The tide is definitely turning in that the major abilities of a small number of other audit firms are being considered for significant public audit work," she said.
Grant Thornton was recently named Auditor of the Year (Outside the Big 4) at the Real FD/CBI Finance Directors' Excellence Awards - an honour decided by a nationwide customer service survey of companies.
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