Middlesbrough have been approached by fellow Championship clubs who harbour suspicions that their pre-match training sessions may also have been spied on by Southampton.

The English Football League has charged the south-coast club with misconduct after a member of Tonda Eckert’s backroom was allegedly caught breaching regulations by filming and making audio recordings of one of Kim Hellberg’s final practice sessions before his Middlesbrough side faced Eckert’s Southampton in Saturday’s playoff semi-final first leg at the Riverside Stadium. As Hellberg prepares his players for Tuesday’s second leg at St Mary’s Stadium with the score goalless, Championship rivals are understood to be examining any available CCTV training-ground footage from recent weeks.

Images of the alleged spy, believed to be a Southampton first-team analyst, being apprehended by Boro staff at the team’s Rockliffe Park training base near Darlington on Thursday have been widely circulated. “I think every club in the Championship should be angry because, who knows,” said Hellberg after Saturday’s game. “It’s wrong. It’s just wrong.”

Given Boro are in possession of what they consider “strong” CCTV evidence of the alleged offence, it is understood Southampton will not contest the charge at an independent disciplinary commission scheduled to convene within the next fortnight. They may, however, try to claim the man in question was an intern, desperate to impress and acting unilaterally as a lone wolf.

Meanwhile, other second-tier clubs have shared with the Guardian their surprise at the ease with which Southampton adapted to supposedly unexpected team shapes and appeared able to second-guess set-piece routines during an unbeaten run of 19 league games towards the end of the season. That may, however, have been down purely to the tactical skill of Eckert, a 33-year-old former analyst of the German national team who took charge last November.

Hellberg was adamant on Saturday, however, that his team had been the targets of “cheating”. Moreover, the Swede is adamant that, with the prize for winning the playoff final and joining the Premier League estimated to be worth about £220m in additional income, a fine would be insufficient punishment for Southampton should they be found guilty of spying, or indeed a future deterrent for other clubs.

Middlesbrough are also expected to remind the commission – which has been assembled and will be chaired by a lawyer – that in 2024, the Canada Women coach, Bev Priestman, and two of her staff were banned from football for 12 months after spying on New Zealand at the Paris Olympics. Canada were also docked six Olympic points. And although Leeds were only fined £200,000 after one of Marcelo Bielsa’s staff was spotted sitting in a tree during a clandestine attempt to watch Derby train in 2019, the EFL then had no specific anti-spying rule. A new regulation has been subsequently introduced that offers the EFL the power to impose fines, deduct points and expel teams from competitions.

A Southampton statement released on Friday, after the club had been charged by the EFL, read: “We can confirm that we will be fully cooperating with the League throughout this process. Given the ongoing nature of the matter, the club is unable to comment any further at this time.”