David Cameron has said he cannot remember “in any detail” being briefed about the Horizon scandal while he was prime minister. The foreign secretary, who was in No 10 from 2010 until 2016, faced questions on what he did to stop the growing scandal following reports that the Post Office could be facing a £100m bill and insolvency after claiming tax relief for its compensation payments to post office operators. More than 700 post office operators were imprisoned, vilified and left bankrupt by incorrect prosecutions based on the Post Office’s unreliable Horizon accounting system. Lord Cameron said anyone who had been involved in government in the past two decades had to be “extremely sorry” for the miscarriage of justice. “This is an appalling miscarriage of justice and anyone who’s been involved in government in any way over the last 20 years has got to be extremely sorry, as I am, about what has happened,” he told Sky News’ Sunday Morning with Trevor Phillips show. But he added: “I don’t recall in any detail being briefed or being aware of the scale of this issue. We’ve got to get to the bottom of it, and that’s what inquiries do, they can look at what were ministers told, what information was put in front of them, what did they decide – because it’s hard to remember every letter and piece of paper put in front of you.” Ed Davey, the Liberal Democrat leader who served as Cameron’s postal affairs minister in the coalition government, has faced criticism for refusing to apologise. Keir Starmer has also been forced to deny he was aware of CPS prosecutions against post office operators when he was the director of public prosecutions. The former prime minister Theresa May has faced criticism for allegedly pushing for Paula Vennells, the CEO of the Post Office during the scandal, to be awarded a CBE despite concerns being raised on the honours committee due to the Horizon scandal, the Sunday Times reported. One senior civil servant at the time said there was a view that Vennells had “inherited” the Horizon problem and was “clearing up, rather than being the cause”, the paper said. The government has already taken the unprecedented step of announcing a plan for the mass exoneration of post office operators in England and Wales caught up in the scandal, which captured the public’s attention after the ITV dramatisation Mr Bates vs the Post Office. Kevin Hollinrake, the postal affairs minister, has argued that figures at the Post Office who are found to be responsible for the scandal should be jailed, saying it would be the “ultimate deterrent”. Cameron would not go so far but said anyone found to have broken the law “should face criminal charges”. “We’ve got to get to the bottom of who is responsible for what and who should be accountable,” he said. “And, if it involves lawbreaking, we have an independent judicial system in this country and, if people have broken the law, they should face the consequences.” A Lib Dem source said: “The attempt by the Conservative party to make political capital off the back of this historic miscarriage of justice has been exposed as breath-taking hypocrisy. Ed Davey met with Alan Bates and was the first minister to do so. Tory ministers then refused to meet Mr Bates even as the scale of the scandal became clear. “There are now serious questions for the government to answer about why they handed a CBE and Cabinet Office role to Paula Vennells while refusing to meet Mr Bates.”