An Oxford graduate is suing the university for £1m claiming the “appallingly bad” and “boring” teaching cost him a first-class degree and prevented him from having a successful career.

Faiz Siddiqui, who studied modern history at Brasenose College, told the high court he believes he would have had a career as an international commercial lawyer if he had been awarded a first rather than the 2:1 he achieved 16 years ago.

If he wins, the case could open the floodgates to similar claims from students complaining about inadequate teaching, unsuitable accommodation and poor decisions.

Siddiqui, 38, who trained as a solicitor after university, says his life and career have been blighted by his failure to obtain a first when he graduated in June 2000. He said he underachieved in a course on Indian imperial history during his degree because of “negligent” teaching which pulled down his overall grade.

He is bringing a loss of earnings claim of at least £1m against the chancellor, masters and scholars of Oxford University, which is seeking to have the claim struck out.

According to a report in the Sunday Times, Siddiqui suffers from insomnia and depression which his barrister, Roger Mallalieu, puts down to his unexpected failure to gain a first.

Mallalieu told the high court that his client’s lesser grade “denied him the chance of becoming a high-flying commercial barrister”.

Oxford University argues that the claim is baseless and should be struck out because of the number of years that have passed since Siddiqui graduated.

The university admitted it had “difficulties” running the module in the year Siddiqui graduated because half of the teaching staff responsible for Asian history were on sabbatical leave at the same time.

Siddiqui has said the standard of tuition he received from Dr David Washbrook declined as a result of the “intolerable” pressure the historian was placed under. In the academic year 1999-2000, four of the seven faculty staff were on sabbaticals and the court heard from Siddiqui’s barrister that it was a “clear and undisputed fact” that the university knew of the situation in advance. He told the judge that of the 15 students who received the same teaching and sat the same exam as Siddiqui, 13 received their “lowest or joint lowest mark” in the subject.

Mallalieu told the court: “This is a large percentage who got their lowest mark in the specialist subject papers. There is a statistical anomaly that matches our case that there was a specific problem with the teaching in this year having a knock-on effect on the performance of students.” He added: “The standard of teaching was objectively unacceptable.”

A judgment is expected later this month and Siddiqui’s legal team claimed he was “only one of a number of students who no doubt have proper cause for complaint against the university in relation to this matter”.