A former Royal Marines captain is aiming to neutralise Johnny Mercer’s electoral “trump card” of having a military service record, after being selected by Labour to stand against the veterans minister at the next general election. Fred Thomas, 31, who spent seven years in the elite commando force, will be attempting to overturn a nearly 13,000 Conservative majority in Plymouth Moor View. In his first national media interview, Thomas said he had been partly driven to politics by his Tory opponent’s claims to be helping veterans, many of whom are struggling to survive. “I would love to see Johnny Mercer lose his seat to anyone, even if I hadn’t left the Royal Marines to do this, because he uses veterans as a huge campaigning tool. He just hasn’t delivered. “Veterans are really struggling with the cost of living crisis and he is part of the government that caused that. “While I was serving, it was incredibly frustrating, time and time again, to hear someone painting themselves as a great champion for veterans’ rights when this was going on,” he said. His combative words will set up an intriguing political battle for the seat in south-west Devon, in a city that is home to many veterans and is built around a naval base. Mercer, 41, a former captain in the Royal Artillery, took the seat from Labour in 2015, and increased his vote share in 2017 and 2019. Conservative leaflets have sought to highlight Mercer’s 10-year career in the army. He has written a book about his three tours of Afghanistan, in which he referred to his time working with special forces. Thomas said he hoped that facing an opponent from the armed forces might push the Conservatives and Mercer to talk about their political records instead. “I am sure he finds me threatening, and I think he will know that his trump card that he has used for the last eight years he has been an MP he no longer can use,” he said. Thomas, one of five children born to a civil servant and a teacher, was a pupil at the top public school Winchester college before reading religion, politics and ethics at King’s College London. Thomas learned to read and write Arabic, studied in Egypt shortly after the Arab Spring, and was there while there was a coup against the Muslim Brotherhood. After signing up to the military, he became the Royal Marines’ light heavyweight boxing champion and was deployed to train in Arctic warfare and worked in nuclear security on Faslane naval base in Scotland. He also served in combat missions before leaving the corps in February, he said, but remains tightlipped about the details. Asked if he served with special forces, as sources have claimed, Thomas declined to comment. Thomas said his primary motivation for leaving the corps for politics was because he had “a sense of public service” and realised that the UK’s economic and political institutions were breaking down. “There was this assumption when we [the Royal Marines] were engaged in international development or international security work that the UK has got the basics sewn up. But increasingly I saw that it was not the case,” he said. He indicated that the next government should recommit to spending 0.7% on international development. “Whether we like it or not, countries do look to us because we do have experience of driving change in an international sphere,” he said. The Labour party appears to be quietly elated at having bagged a presentable former officer. One party insider said Thomas was “a younger, better looking and more accomplished version of Mercer”. Thomas acknowledged that Labour HQ was throwing resources at the seat, because it was precisely the kind that would have to fall if Starmer was to form the next government. “I’ve actually got two Labour party staff video makers with me in Plymouth. We are off the ground,” he said on Thursday. Thomas said he expected a bruising election campaign, given Mercer’s fondness for public confrontations, often on social media. Shortly after Thomas’ selection as Labour’s candidate, Mercer’s wife, Felicity Cornelius-Mercer, claimed in a tweet that her husband’s war record was more impressive than his new opponent. “Fred doesn’t compare to JM’s frontline combat,” she wrote. Thomas said he was prepared for intense scrutiny and criticism in the lead-up to the election. “I get it. It is a Royal Marines captain against an army captain. I understand that as a story. But this is about everyone in our community being served by someone who supports policies that will improve their lives,” Thomas said. • This article was amended on 14 August 2023. An earlier version said that Fred Thomas had been a “senior army officer” when he was a captain in the Marines.