An investigation has been launched into alleged "financial irregularities" at a subsidiary of long-established Birmingham accountants Wenham Major, the firm has announced.

The practice revealed it is conducting an inquiry into its private client tax planning operation run by executive chairman John Joyce, a well-known figure in the city's accountancy sector.

He was said this week to be absent on health grounds and facing proceedings by the firm as a result of the inquiry's preliminary findings.

Wenham Major said the inquiry was internal with the help of lawyers and forensic accountants and neither the police nor accountancy regulators were involved.

Based in Cornwall Street, the firm - full name Wenham Major Global Capital Partners - is one of the largest and oldest accountancy practices in the country. It is also one of the fastest-growing and has offices in London's Mayfair, Dubai and New York.

Ammar Azam, who owns the business jointly with Mr Joyce, said yesterday he had "discovered financial irregularities" at subsidiary business Wenham Major Private Client.

Private Client operates as a tax planning business on behalf of a small number of wealthy clients, the majority in London.

The subsidiary business was established by Mr Joyce and operated and controlled by him with three staff. The alleged irregularities came to light after Mr Joyce became ill and asked Mr Azam to look after the Private Client business.

"John Joyce is currently the primary subject of the company's investigations," Wenham Major said in a statement. "As a result of preliminary findings, it is the intention of the company to issue proceedings against John Joyce. John Joyce's staff are co-operating fully."

The statement went on to say the main Wenham Major accountancy business, headed by Mr Azam, is in no way implicated in the inquiry.

It "continues to operate in a professional manner and is not the subject of any suspicion," the statement added.

"The accounting practice is profitable, growing and is meeting its operational and financial targets."

Mr Joyce was said to be in hospital suffering from a stress-related complaint and to be uncontactable. It is believed that except for a brief conversation with one of Wenham Major's legal advisers, he has not yet been questioned as part of the inquiry.

Mr Azam would not disclose the extent of the financial irregularities but it is understood that clients' money is not involved.

Wenham Major Private Clients undertakes tax advice on a fee basis and does not handle funds.

Wenham Major's 200 staff were told about the inquiry at a briefing on Wednesday.

"It is my intention to inform the rest of the staff and put them in the picture because it is the right thing to do," Mr Azam said.

"They are our primary concern at the moment."

Wenham Major was founded in Cherry Street, Birmingham, by Alfred Ebenezer Wenham in 1867. Mr Joyce joined the practice in 2003 as chief executive and together with Mr Azam took it over in a management buy-out in 2006.

Since then it has made a number of acquisitions, opened offices in Dubai and New York and has more than doubled its annual fee income to more than £22 million.