The UK defence secretary, Ben Wallace, has accused Prince Harry of “boasting” about the number of people he killed while on tour in Afghanistan and “letting down” his fellow service personnel. Wallace, a former soldier, joined other high-profile veterans to have criticised the Duke of Sussex’s claim he killed 25 Taliban soldiers while serving with the British army. Though Wallace said it was up to each former service personnel member to “make their own choices about what they want to talk about”, he said it was not something he would have divulged about his own time as a captain in the Scots guards. “The armed forces is not about a tally,” Wallace told LBC radio on Thursday. “I frankly think boasting about tallies or talking about tallies … distorts the fact that the army is a team game.” Wallace said serving in the military was a “team enterprise” and that for any person to go into combat they would have been supported by “hundreds of people behind them” – whether in a headquarters back in Britain or by the Royal Logistic Corps who helped them get there. Emphasising he was voicing a personal view, Wallace said he believed the success of a person’s time in the armed forces was not measured by “who can shoot the most or who doesn’t shoot the most”. He added: “If you start talking about who did what, what you are actually doing is letting down all those other people, because you’re not a better person because you did and they didn’t.” The prince recounted in his memoir, Spare, his time as a gunner in an Apache attack helicopter while on his second tour in Afghanistan in 2012. Harry wrote that “in the era of Apaches and laptops” it was possible to establish “with exactness how many enemy combatants I had killed”. He added: “It seemed to me essential not to be afraid of that number. So my number is 25. It’s not a number that fills me with satisfaction, but nor does it embarrass me.” Later, the prince acknowledged he had dehumanised those who he had shot in battle: “When I found myself plunged in the heat and confusion of combat I didn’t think of those 25 as people. They were chess pieces removed from the board. Bad people eliminated before they could kill good people.” Retired senior veterans have previously criticised the prince for his comments, and said it could put his own security at greater risk. Wallace also appeared to aim a barb at his Conservative colleague Johnny Mercer, the veterans minister, who had suggested his recent public interventions calling for more funding for the Ministry of Defence were a concerted lobbying effort, and dismissed suggestions of paltry defence spending. Wallace described Mercer, who attends cabinet but is not a secretary of state, as a “junior minister”, adding: “Johnny luckily doesn’t have to run the budget. You know, I have a defence budget that has to deal – like all the other budgets – with inflation, with changes to threat, and I have to just deal with that.” Wallace said he had a department of 224,000 people, while 12 people worked in Mercer’s office.