A former finance director at Prestwick Airport has claimed he was sacked for exposing allegations of fraud, bribery and collusion at the state-owned site.

Derek Banks claims he told bosses about potential corruption within its procurement process and was dismissed soon after for blowing the whistle.

The allegations, which were exposed at an employment tribunal hearing, include claims a third party acting on behalf of the airport kept its relationship with a bidder for runway resurfacing work a secret.

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It also emerged that the same contractor had sought bids for work "in excess of the airport's requirements".

Mr Banks, 50, from East Kilbride, has lodged claims with the tribunal for unfair dismissal and being treated unfairly for making a public interest disclosure.

The hearing in Glasgow yesterday was told that Mr Banks submitted a report to airport bosses detailing his concerns in March this year and also asked for an audit to look at any impropriety.

However, his audit request was refused and he was dismissed a month later.

Airport officials claim he was dismissed because of poor performance, but Mr Banks's position is that there were no issues with his work before he spoke up on the allegations.

The airport's non-executive chair Andrew Miller told the hearing that he received the report and agreed it included claims of potential fraud, bribery, collusion and conflicts of interest.

Mr Bank's Solicitor Ingrid McGhee put it to Mr Miller that it showed that the third party, Halcion Ltd, had not been honest about its links to bidder Breedon Aggregates.

Asked if the report concerned him, he said: "Yes it did concern me, but we took the party out and rescored them and they still would have won the contract irrespective of what we subsequently found out."

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He was also asked if it concerned him that what was asked by Halcion was "far higher than what was required". He replied it did.

Miss McGhee asked: "Are you willing to confirm if the allegations of fraud, collusion, bribery and conflicts of interest in respect of the runway resurfacing matter were confirmed?"

Mr Miller replied: "Conflict of interests, yes. Collusion, maybe. But fraud and bribery, no."

The tribunal heard that Mr Banks also made a number of claims involving misuse of the procurement process by the airport's operations director Jules Matteoni and allegations of expenses misconduct by HR director Sonia Rafferty, who denied any wrongdoing on her part.

However, Mr Miller argued that Mr Banks was sacked because of a "lack of engagement within in the business and poor stewardship".

He also said the airport had concerns about Mr Banks's involvement with a female member of staff.

The tribunal heard that an email passed between Mr Miller and the airport's chief executive Stewart Adams said that Mr Banks was "not a team player" and had undermined his colleagues.

It also stated that other directors had given him the nickname "devious Derek".

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In her closing submission in the hearing - which was to decide if Mr Banks should be allowed to keep his job until a decision is made in his case - Ms McGhee said that when her client raised concerns about Ms Rafferty and Mr Matteoni, Mr Miller told him to "back off Sonia and Jules".

She also claims he was told that a "nail with its head showing will have it knocked off" and from that point on Mr Banks felt his "card was marked".

The lawyer added that Halcion had not been "open and transparent about their relationship with a prospective tender" and that this had a "financial benefit to [Halcion] and Breedon".

She said: "The claimant held a reasonable belief that there was potential collusion, fraud and bribery being carried out by Halcion on behalf of the respondent."

Ms McGhee added: "No other person was actively tackling these issues within the respondents and the claimant ultimately paid the price for doing so with his career."

Brian Campbell, the lawyer acting for the airport, said that many of the claims made by Mr Banks were not protected disclosures.

He also claimed that the director was not the original source of the claims about the Halcion and Breedon contracting issue.

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Mr Campbell said there was "no apparent credible motive why he would be dismissed for his part in the investigation".

The lawyer added that Mr Banks was ultimately dismissed because of "his perceived lack of engagement in his role and poor performance".

A decision on whether or not Mr Banks will be allowed to keep his job in the interim will be issued at a later date by employment judge Shona MacLean.