More than 70 MPs including 40 Conservatives, the former Labour leader Jeremy Corbyn and Liberal Democrat members have forged a parliamentary alliance to oppose Covid identity documents. It came as Boris Johnson suggested the government would move ahead with the scheme and it was announced that pilots of mass testing at large events would take place this month. Four former Tory cabinet ministers including Iain Duncan Smith and Andrew Mitchell are among the group, along with key Labour leftwingers such as John McDonnell, Clive Lewis, Diane Abbott and Rebecca Long-Bailey. The coalition of MPs is backed by the civil liberties groups Liberty, Big Brother Watch, the Joint Council for the Welfare of Immigrants (JCWI) and Privacy International. Johnson has noticeably warmed to the idea of the documents in recent weeks. Government sources have suggested the certificates could be used by businesses as a way to relax social distancing measures inside venues. An interim report on the measure is due to be published on Monday but a pilot event is already planned for 18 April with residents near Wembley invited to apply for 4,000 tickets to the FA Cup semi-final between Leicester and Southampton. Speaking on a visit to Middlesbrough, Johnson said a certificate could be used to prove a person was safe in a number of ways, not just vaccination. For the Wembley event, Brent council said each attender had to return a negative lateral flow Covid-19 test 24 hours before the game and show proof to gain entry. They will also need to take a PCR home test after the event. Johnson suggested businesses would welcome the idea of Covid certificates. “When it comes to trying to make sure that we give maximum confidence to business and to customers here in the UK, there are three things: your immunity, whether you’ve had it before, so you’ve got natural antibodies anyway; whether you’ve been vaccinated; and then, of course, whether you’ve had a test. And so those three things working together will, I think, be useful,” he said. The Labour leader, Keir Starmer, has hinted at Labour’s unease about the system, saying it goes against “British instinct” to show documents to gain access to venues such as pubs, but he has not directly said his party will oppose the idea. The number of Tory MPs opposing the measure would put Johnson at risk of losing his majority, as long as Labour also opposes. Those opposing include Mark Harper and Steve Baker, the leading MPs of the lockdown-sceptic Covid Recovery Group, as well as the chair of the 1922 Committee, Sir Graham Brady, and the former ministers Esther McVey, Harriett Baldwin and David Jones. However, the use of tests, rather than vaccines, to gain certificates could address some concerns. Brady said life should be returning to normal. “Covid-status certification would be divisive and discriminatory,” he said. “With high levels of vaccination protecting the vulnerable and making transmission less likely, we should aim to return to normal life, not to put permanent restrictions in place.” Shami Chakrabarti, the former shadow attorney general and ex-director of Liberty, said the group were opposed to the domestic use of Covid certification. “International travel is a luxury but participating in your own community is a fundamental right,” she said. “So internal Covid passports are an authoritarian step too far. We don’t defeat the virus with discrimination and oppression but with education, vaccination and mutual support.” Jonathan Djanogly, the former Tory frontbencher who has been aligned with the party’s centre-right, said he was concerned about the impact on young people and about the legal implications. “It is beset with legal and human rights minefields,” he said. “It’s also going to be all but ignored by large numbers of traders. And it will mainly affect the same young people who will be last to be inoculated but first to go to pubs.” The Lib Dem leader, Ed Davey, will whip his MPs to oppose the measure and said it was time to turn the tide on “creeping authoritarianism” from the government. “As we start to get this virus properly under control we should start getting our freedoms back. Vaccine passports – essentially Covid ID cards – take us in the other direction,” he said. “Liberal Democrats have always been the party for civil liberties. We were against ID cards when Blair tried to introduce them and we are against them now.” Silkie Carlo, the director of Big Brother Watch, said: “We are in real danger of becoming a checkpoint society where anyone from bouncers to bosses could demand to see our papers. We cannot let this government create a two-tier nation of division, discrimination and injustice.” Starmer told the Daily Telegraph he believed domestic use for Covid certification would become largely redundant. “My instinct is that … [if] we get the virus properly under control, the death rates are near zero, hospital admissions very, very low, that the British instinct in those circumstances will be against vaccine passports,” he said. Michael Gove, the Cabinet Office minister, who is leading deliberations on the policy, met a series of MPs this week before the publication of the interim findings of the panel on vaccine passports, which is due on Monday. Gove is generally seen as a strong supporter of the scheme. But officials and ministers are said to be divided between whether the certification should apply only to mass events, for which there is broad support, or additionally to smaller venues, which is more controversial. As well as the FA Cup semi-final there will also be a pilot on 25 April at the Carabao Cup final at Wembley between Manchester City and Tottenham which is set to have a limited number of fans of the clubs. If the scheme becomes widespread the plan is to make the certification available on a modified NHS app, which would detail whether a person has had a vaccination, or a recent test, or has antibodies to the virus, having previously tested positive.