HSBC discriminated against a gay senior banker while investigating him over allegations of an indecent sexual act, an employment tribunal was told today.

Peter Lewis, the bank’s former head of equity trading, said that HSBC was in a “rush to accuse” and “a rush to judge” after another banker accused him of a lewd act.

Mr Lewis, 46, told the tribunal in East London that the initial investigation into his alleged behaviour was conducted on the premise of “a belief that as a gay man, I was guilty as charged”.

Mr Lewis’ lawyer, Chris Quinn of Littleton Chambers, said in his opening submission that “HSBC's discriminatory predisposition against [Mr Lewis] as a gay man sealed his fate.”

Mr Lewis sued HSBC for £5 million last year, claiming unfair dismissal and discrimination on the grounds of sexual orientation. He lost the bulk of his claims — 12 out of 16 — but after appeals by both sides the Employment Appeal Tribunal ordered a fresh hearing into four of them.

The Stratford tribunal has set aside two weeks to hear the case, which will now focus on whether the way in which HSBC investigated the accusation against Mr Lewis was discriminatory.

The bank denies this and insists that Mr Lewis was treated the same way as any other member of staff.

Today, Mr Lewis told the Tribunal that he had recently learned the details of a separate incident of alleged discrimination at the bank involving a claim of racial discrimination.

Mr Lewis said the strength of the initial evidence in the racial discrimination allegation was broadly similar to the evidence in the claim that he faced.

But, whereas no further action was taken against the banker accused of racial discrimination, his case was referred to an internal disciplinary process that ultimately led to the loss of his job, Mr Lewis added.

Elsewhere, Mr Lewis accused his former employer of ignoring its own “safeguards and procedures [designed] to make sure that an innocent man doesn’t lose his job, his livelihood and his career.”

After some brief questions from Mr Quinn, the remainder of the morning session was taken up with cross-examination from Andrew Hochhauser, QC, for HSBC.

After Mr Quinn raised an early objection to Mr Hochhauser’s line of questioning, Mr Hochhauser told the Tribunal that he took exception to Mr Quinn “seeking to derail his cross-examination so early [on in the proceedings].”

The Tribunal heard a series of increasingly bad-tempered exchanges between the two barristers that included accusations of “snide comment[s]”, “extraordinary insinuations” and “theatrical interventions.”

The case concerns the investigation into an accusation that Mr Lewis masturbated in a shower cubicle next to another male HSBC worker, who, for legal reasons, is referred to as “Mr A”.

Mr Lewis has always denied the incident took place and today said he was the victim of a “poisonous'' and “homophobic” attack.

Mr Lewis joined HSBC in September 2004 with his minimum pay guaranteed at £1.6 million over two years, plus bonuses. He was suspended in November 2004 and fired in February 2005.

Alison Downie of Bindman & Partners is acting for Mr Lewis. HSBC is advised by Allen & Overy.

HSBC declined to comment.

The case continues.

Explore Law

• Columnists

• Law Panel

• Law Reports

• Student Law

Times Recommends

• BGC 'set aside £40m to lure Tullett brokers'
• Legal aid review to ensure value
• Fears as 21 magistrates' courts face closure