The designated safety officer of the Olympic Stadium resigned in May after becoming deeply concerned about the retractable seating and its impact on the structure of the ground’s lower tier, the Guardian has learned.

Chris Baker, an experienced, career stadium safety officer, is understood to have resigned shortly before the concert by the rock band AC/DC, which was held on 4 June, only two months before West Ham United’s first match at the renamed London Stadium.

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One of Baker’s deputy safety officers, Ravi Sharma, who worked at the AC/DC concert, is understood to have raised serious concerns afterwards about the management, policing and stewarding of the crowd at the event and also decided not to work at the stadium again.

Baker is understood to have become concerned about the potential conflict of interest of Newham council, which is the authority legally responsible for certifying the stadium is safe, while it also owns a 35% share and, having loaned £40m towards the stadium’s conversion costs, makes money back from the events it hosts.

Baker, who formerly worked at Brighton & Hove Albion when the club moved into their new Amex Stadium in 2011, and Sharma, whose full-time role is head of safety and security for Stoke City, declined to talk to the Guardian. However, sources with knowledge of their situation said both men voiced their safety concerns internally but believed they were not being taken seriously enough and so took the decision no longer to work at the stadium.

West Ham’s opening matches at the stadium have been overshadowed by complaints that its layout and some of its policing and stewarding arrangements have been inadequate, culminating in ugly scenes and many supporters feeling in danger at the EFL Cup game with Chelsea last week. Initial problems included police not having adequate radio signal around the stadium, and there are worries the stewarding operation is not experienced enough, as many of the 300 stewards who formerly worked for West Ham at the Boleyn Ground have not moved across to Stratford.

On Tuesday the mayor of London, Sadiq Khan, announced an inquiry into the financing of the stadium, which has now cost £752m and been handed over to West Ham for a £15m one-off payment and £2.5m annually, which covers the whole operation and maintenance, including stewarding and policing. Khan’s investigation is particularly focusing on the escalating cost of the retractable seating, constructed over the retained athletics track, which has risen from a projected £300,000 each time to as much as a projected £8m.

Baker, who became the official safety officer in November 2014, was in his post for Rugby World Cup and rugby league matches held last year, and for the Race of Champions motor racing event for which the seats over the track were retracted. The system now installed involves the seats being moved manually rather than hydraulically, and Baker is thought to have been concerned the track itself and parts of the lower tier had been damaged in the process. When the issue was not dealt with to his satisfaction, his concerns are said to have grown over Newham council’s oversight role, and he resigned.

Sharma, who was one of several deputy safety officers and worked at the London Stadium on a contract when fixtures and duties at Stoke City’s bet365 Stadium permitted, took the role of safety officer at the AC/DC concert, the Guardian understands. He is said to have been unhappy about the levels of policing in the Olympic Park itself, the approach to the stadium and around it, and the management of the crowd when entering and leaving.

Since 96 people died at Hillsborough in 1989 and the subsequent report by Lord Justice Taylor on safety, all major stadiums must be certified as safe according to strict statutory standards applied by the relevant local authority, and must have a full-time, qualified, designated safety officer. Newham council’s position is not unique in being the legal safety licensing authority for a stadium in which it has an ownership, and such potential conflicts of interest have to be managed to ensure there is no compromise with safety.

A Newham council spokeswoman said its co-ownership of the stadium “in no way impacts on [our] role in monitoring safety which we take very seriously”. The council’s safety role, she said, is fulfilled by specialist, qualified officers, while its commercial interest in the stadium is managed by the ownership vehicle E20 which, she said, “operates independently”.

West Ham and LS185, the contracted stadium operator for whom Baker and Sharma were working, stressed the safety of its arrangements and experience of the officers who replaced them. The stadium’s head of safety and security, Steve Riley, is a former match commander at Chelsea and safety officer at Fulham, and he and the safety officer, Peter Smith, are former Metropolitan police officers. Graham Harris, who replaced Sharma as a deputy safety officer, previously worked for three years in safety and security management at Wembley stadium.

The stadium owner E20, owned 35% by Newham council, 65% by the London Legacy Development Company – whose chairman, David Edmonds, resigned on Thursday following Khan’s announcement of an inquiry – appointed the former Metropolitan police commissioner Chris Allison in September to oversee safety and security, following the crowd problems at West Ham’s first matches.

A club spokesperson said: “West Ham United are satisfied with London Stadium’s current safety team and their experience to manage the safety at our matches.”

The Sports Grounds Safety Authority, a government agency responsible for overseeing compliance with the law, sits on the London Stadium’s safety advisory group, which is chaired by Newham council. A spokeswoman said despite “challenges for West Ham moving into the stadium”, the body has “no reason to doubt the local authority’s commitment to public safety”.