Image copyright Getty Images Image caption Former clients accuse RBS of document tampering, which the bank denies

Former business clients of the Royal Bank of Scotland are accusing the bank of systematically manipulating documents to cover up wrong doing.

In an exclusive interview with the BBC, a former RBS employee has come forward to support allegations of document manipulation within the bank.

RBS says it categorically denies document manipulation and forgery.

Mark Wright started working for NatWest Bank in 1988 and was still there in 2000 when it was taken over by RBS.

In 2005, Mr Wright accused two former RBS colleagues of concocting bogus complaints purportedly from five of his customers.

He says the employees were from the bank's Group Compliance Unit established to deter misconduct and malpractice in RBS. He referred to the unit as the bank's "police".

Mr Wright's five customers later submitted statements contradicting the bogus complaints. The two accused compliance staff subsequently left the bank.

RBS customers who allege wrongdoing

The BBC has spoken to a number of businessmen and financial advisers who allege document manipulation and forgery by RBS all of which allegations the bank denies. They include:

Former Metropolitan police sergeant Andy Keats claims that fraud by RBS destroyed his security business in 2007 and could cost him his home. He claims the bank has falsified documents relating to him including the transcript of an important telephone conversation. In a statement RBS acknowledges its transcript does not constitute a word-for-word written record of the recording but categorically denies falsifying customer records to suit its purposes

Builder Clive May, from north Wales, claims RBS deliberately made his company insolvent in 2011 and is accusing the bank of fraud. He is suing RBS for allegedly selling him a government loan known as an Enterprise Finance Guarantee (EFG). He and others claim the bank committed fraud against the government as well by securing EFGs for customers who were not entitled to them. Mr May says the bank has doctored documents to cover up its misconduct. The bank insists the particular document complained of is actually a draft of the final version issued and held by Mr May and therefore, there are two separate documents

Steve Middleton, from Hull, represents customers who claim they have been defrauded by RBS. He says the bank records he has received from RBS that related to at least three of his clients have been manipulated. He said the documents appear to have been cut and pasted from the bank's main document database, the Relationship Management Platform System. RBS said it didn't have enough information to respond to Mr Middleton other than to reiterate its denial that it manipulates customer records.

Mr Wright told the BBC that the bank failed to properly investigate the complaints or accord him the status of whistle-blower.

"I had five individual customers who all came forward to me stating that the wording and conversations with this member of staff from group compliance were not their words, so effectively the telephone transcripts didn't reflect what the customer was saying."

Mr Wright said as a senior manager he had a duty to report the falsifications.

"I told my line manager this because he had been affected by the negative rating that Group Compliance had given me over these fictitious five customer complaints and falsifying the customer care calls so I decided to contact them all and the behaviour was the same with all five."

'I was suspicious'

Mr Wright said he learned later from colleagues that such misconduct was not uncommon in the bank's Compliance Unit.

"I discovered through a member of staff from Group Compliance that it would be common practice that they would falsify files if they needed to create a certain picture."

Mr Wright said he became increasingly concerned about the way the bank handled allegations of wrongdoing and had wanted a full external investigation because of the serious nature of his allegations.

"I was suspicious of wrong doing from 2005 to 2012," he said.

Mr Wright claims his standing within the bank suffered enormously as a result of his action.

His employment status within RBS was changed to "undesirable" when previously he had been classed as "excellent". Bonuses were also stopped.

In 2013 Mr Wright finally took redundancy after his GP diagnosed him with long term mental health issues. The bank upheld one of his grievances.

A RBS spokeswoman said the bank was aware of these concerns being raised previously and that they had been thoroughly investigated and responded to.

She denied there had been systematic document tampering at the bank.

Image caption MP Norman Lamb has concerns over the way Mr Wright's allegations have been treated

Mark Wright lives in the constituency of North Norfolk represented by former government minister, Liberal Democrat Norman Lamb. Mr Lamb said he has written to RBS five times to demand a meeting about Mr Wright's allegations.

How high did this go?

He said: "My fear is that it appears to be more than a few rotten apples behaving badly. There appears to be an institutional culture here that facilitated this corrupt practice. That's the allegation.

"And the way in which they dealt with a whistle-blower, who ought to actually be respected and treated with the utmost seriousness, instead they pushed him through a very long process, the wrong process."

Mr Lamb said: "Treating it as a grievance not going through the proper whistle-blowing process and allowing that individual to be destroyed rather that treating seriously the allegations that he raised and that for me begs the question. How high did this go? Did it go to the very top of the bank? And why are the current leadership not prepared to examine these really serious allegations thoroughly?"

Image caption James Hayward, chief executive of the group representing former RBS business clients says they are suing RBS for alleged document tampering

The BBC has also spoken to former business clients of RBS, who also claim fraud and document tampering.

The RGL management group is representing many in a planned court action. At least 300 companies plan to sue the bank.

James Hayward, chief executive of RGL, told the BBC that the companies were suing RBS on ten grounds of alleged malfeasance including document tampering.

"In most cases the end result of what the bank did to their people was the total destruction of their businesses and people's lives.

"These people were intentionally financially and emotionally destroyed. Their only mistake was to trust the bank that they thought was there to help them succeed."

He said he had also seen evidence of document manipulation by the bank.

"If anybody manipulates documents or falsifies documents or forges documents it can only be for two reasons, and that's to perpetuate a fraud or to cover up a fraud," Mr Hayward said. "There's no other reason for doing it. We have come across it. It's just another instance of an unbelievably appalling sort of corporate conduct."

RBS says it takes any allegations of misconduct very seriously. It's aware of specific allegations, which have been investigated thoroughly in the past by the bank and, in many instances, externally through bodies such as the Information Commissioner and the courts.

The bank added that it had found no evidence to support these customers' allegations and categorically denied manipulating or falsifying customer records to suit its purposes.

You can listen to Andrew Hosken's full report for BBC Radio 4's World Tonight on iPlayer.