A company chairman is taking Royal Bank of Scotland to the financial ombudsman, complaining that the bank denied him access to the company's bank account and refused to speak to him, after being wrongly told he had resigned.

Andrew McAllister, a former CBI council member, says RBS relied on a mandate form removed his access to the accounts, then refused to accept that he had neither resigned nor been given the required notice of a meeting or a resolution to remove him from the board.

Mr McAllister, chairman and 50% shareholder of software developer Orion Practice Management Systems, which employs 10 in Glasgow, made a routine call at the RBS business centre in Bath Street last October.

"I was informed I was no longer an authorised signatory so she could no longer assist me," he told The Herald. "I tried to obtain further assistance and clarification, but was told no one was available to help me."

Mr McAllister next tried the Gordon Street branch and discovered that the account manager was based at Kirkstane House in Glasgow. "I called there and tried to meet the manager but was turned away and told they did not meet customers at this office," he said. "I called to arrange a meeting but was told neither the manager nor his assistant were available."

When he asked who was instructing the bank, the chairman was told this could not be divulged due to data protection laws.

Nobody would see him or speak to him and told him he ought to seek legal advice.

Mr McAllister said: "I sought legal advice and was told it was impossible for me to be legally removed from the mandate without my consent."

It emerged that both RBS and Companies House had received forms from Orion informing them that Mr McAllister had resigned from the board on September 22 and was no longer a director, following a board meeting.

Mr McAllister, however, says no properly constituted meeting had been held. Companies House confirmed he was entitled to receive notice of any board meeting, and that, further, Section 168 of the 2006 Companies Act requires a special resolution with proper notice for the removal of a director.

Following representations from Mr McAllister, Companies House agreed that Orion's right to use only code-protected electronic filing would be withdrawn while the dispute continued. That allowed Mr McAllister to record his own reappointment as a director from September 22, the day he had supposedly resigned.

On December 16 Mr McAllister appointed his father to the board and on January 4 convened a board meeting at which he was restored as a signatory to the banking mandate.

RBS, however, refused to accept the new mandate, saying it was not properly signed, and the bank was "not comfortable" with the quorum at the board meeting. In its formal reply to the complaint last month, the bank said that it had "acted appropriately" throughout.

An RBS spokesman told The Herald the bank did not take sides in internal disputes, and had acted in full accordance with its obligations.

Peter Knapp, director at Orion, said it was "entirely an internal matter".