Image copyright BT

The boss of BT's Continental European operation is to resign after the firm was forced to write down the value of its Italian unit by £530m after years of "inappropriate behaviour".

BBC business editor Simon Jack said Corrado Sciolla was expected to resign shortly.

BT's shares plunged 21% after revealing the Italian scandal would cost far more than the £145m initially anticipated.

It also warned it would affect its results for the next two years.

The investigation of BT's Italian business, which included an independent review by accountancy firm KPMG, found improper accounting practices and "a complex set of improper sales, purchase, factoring and leasing transactions".

It added: "These activities have resulted in the overstatement of earnings in our Italian business over a number of years."

Image copyright Getty Images

From 2006, Mr Corrado was chief executive of BT Italy before his remit expanded in 2011 to include France.

In January 2013, he was appointed as president of BT's Continental Europe operation, where he reported to Luiz Alvarez, the chief executive of the company's global services business.

Market 'jitters'

In addition to its problems in Italy, BT also said the outlook for the UK public sector and international corporate markets had "deteriorated".

As a result, BT now expects operating profit for the current financial year to be £7.6bn, compared to previously guidance of £7.9bn, and revenue to be flat. It also forecasts that both sales and profit will be flat for the year to March 2018.

BT's shares dropped sharply as soon as trading began, and by midday were down 18% at 313.55p.

BT has an estimated one million small shareholders after becoming one of the first state-owned business to be privatised under Margaret Thatcher's government.

George Salmon, equity analyst at Hargreaves Lansdown, said: "With the group's net debts pushing £9.6bn following the acquisition of EE, and a review of the how to fund the £9.5bn pension deficit coming up in June, there were already a few jitters around the stock, so this was the last thing the group needed."

Allegations of "inappropriate behaviour" at BT's Italian operation first emerged last summer before the company began conducting an investigation in October.

BT group chief executive Gavin Patterson said: "We are deeply disappointed with the improper practices which we have found in our Italian business.

"We have undertaken extensive investigations into that business and are committed to ensuring the highest standards across the whole of BT for the benefit of our customers, shareholders, employees and all other stakeholders."

Image copyright Getty Images

Analysis: Simon Jack, business editor

It's a bad day at the office for BT chief executive Gavin Patterson.

He is £2m poorer, as his 2.8 million shares are down 72p each, or nearly 20%.

That's after the shares were hit by a double whammy of a bigger-than-expected hole in its Italy accounts and lower-than-expected business from the public sector and international corporates.

It's not just him. Nearly a million small shareholders are also out of pocket today. As one of the biggest privatisations of the 1980s, BT still has a small army of people who bought the shares and have held them ever since.

Nevertheless, owning BT shares since privatisation has been a pretty good experience over the last 30 years. The share price has quadrupled in that time, but that is not the whole story: BT has paid steadily rising dividends.

For those investors who chose to reinvest their dividends back into more BT shares - which some did, but not all - an initial investment of £1,000 would now be worth more than £10,000.

Not a bad return, but less than the comparable return on the wider index - the FTSE 100 - over the same period.

BT said it had suspended a number of BT Italy's senior management team who have now left the business. These include former chief executive Gianluca Cimini and chief operating officer Stefania Truzzoli.

The BBC has learned that the company will examine whether to claw back any bonuses paid to them over the two-to-three-year period in which major accounting irregularities have been detected.

It has appointed a new chief executive of BT Italy who will take charge on 1 February.

The company said that the new chief executive would review the local management team and "will work with BT Group ethics and compliance to improve the governance, compliance and financial safeguards in our Italian business".

The Financial Reporting Council (FRC), the UK's accountancy watchdog, said it was considering looking into the matter.

"We are aware of BT's statement about its review of accounting issues in its Italian business and we will consider if these matters require the FRC to investigate whether the auditors and accountants at BT fulfilled their duties," it said.

BT's management may lose out financially following Tuesday's shock announcement. It said: "The BT Group remuneration committee will consider the wider implications of the BT Italy investigation."

It added: "We are conducting a broader review of financial processes, systems and controls across the group."