One of Scotland's highest-profile chartered accountants has described as "excessive" the ruling that led to his being struck off by the professional body, the ICAS.

Eamonn Rice, a former partner and head of financial services at Ernst & Young in Scotland and Northern Ireland, and "special projects" manager at Tesco Bank, was expelled from the Scotttish accountants' institute last month after he "fraudulently prepared a letter" by forging the signature of an insolvency practitioner in a bid to prevent Bank of Scotland from repossessing his luxury home.

There is no criminal offence of forgery in Scotland but a former procurator fiscal told the Sunday Herald that the attempt to mislead the bank's solicitors may constitute the crime of "uttering a false document" under Scottish law. However, a Crown Office spokesman said he was unaware of criminal proceedings being brought against Rice.

In an email to the Sunday Herald, Rice maintained that he "had always challenged and objected to the Institute's view that the letter in question back in 2009 was 'fraudulently prepared'. I believe that the Institute's reaction to the circumstances has been excessive".

He also stressed that "the matter in question related to personal discussions with my bank, not to any professional work".

Rice, 47, is understood to have used "Hunter's Moon", his £1.2 million mansion, in Edinburgh's Braid Hills district, as collateral on Mform's borrowings.

In 2006, the accountant, known for his extravagant lifestyle, persuaded luminaries of Scottish finance to back Mform, a start-up web-based business that traded on providing straightforward and honest mortgage information in a market seen as rife with hidden charges. But the business collapsed in February 2009 after the UK housing market slumped. Peter Anderson, chairman of the ICAS disciplinary tribunal, described Rice's behaviour as "seriously reprehensible", pointing out that it "fell well below the standards expected by the public and the profession of a chartered accountant".

The ICAS tribunal ruled that honesty and integrity were essential qualities in accountants, who "ought to be completely trustworthy".

The expulsion notice, published last month, said: "In light of the serious view taken of Mr Rice's conduct, the tribunal determined that the only finding it could reach which satisfactorily met Mr Rice's conduct was that he be expelled from the Institute."

Originally from Northern Ireland, Rice, a former financial services partner with PwC, Arthur Andersen and Ernst & Young, resigned from E&Y Scotland and Northern Ireland in December 2005. The following year, he launched Mform, with ambitions to take a significant slice of the UK mortgage market.

He and colleagues raised about £12m from investors, including the asset management group Artemis, the former Scottish Widows chief executive Mike Ross, and the former SWIP chief executive Bill Main. These investors lost their shirts when Mform went into administration in February 2009.

Ex-colleagues and backers of Mform last night expressed astonishment at Rice's expulsion from the ICAS, insisting there had been no evidence of impropriety when he was running Mform in 2006 to 2009. One ex-colleague said: "I am astounded. It beggars belief."

Mike Ross, a former director of Mform who  lost a significant sum when the business collapsed, said: "I didn't know about that. In my time as a director of Mform Holdings everything was done properly and professionally."

On Mform's collapse Ross, a former deputy chief executive of Lloyds TSB, said: "It was a very good business idea but the downturn in the housing market meant it lost its unique selling proposition."

Lindsay Whitelaw, a partner in Artemis Investment Management, shrugged off the company's failure and the reported £5m Artemis had lost. He said there had been absolutely no evidence of any management impropriety at Mform, adding: "Eamonn had a strong CV and put a lot of money into the venture personally."

One person familiar with the situation said: "Eamonn has paid a very high price for a moment of stupidity. I have seen a fair number people who, when under a great deal of pressure, have done things they would never do in a rational moment."

At an ICAS disciplinary hearing on May 11, 2011, Rice was found guilty of professional misconduct, given that he had forged a letter from RSM Tenon's Tom MacLennan, then the joint administrator of Mform Holdings. Rice then sought to use this letter to persuade the bank he was eligible for a dividend from Mform's administration. He gave a copy to the Bank of Scotland's solicitors in a desperate bid to persuade them to stop court proceedings against him.

Rice sought to have ICAS's tribunal ruling overturned at appeal. At a tribunal last August he claimed the original ruling was "manifestly excessive" and sought to have his expulsion kept under wraps. But he failed on both counts. The tribunal's original decision of May 11, 2011 was upheld and he was ordered to pay £5000 in costs.