The former Lib Dem leader Sir Vince Cable has labelled Post Office managers “thugs in suits” and claimed he would have got to grips with the Horizon IT scandal if MPs campaigning for branch owner-operators had bothered to have in-person meetings with him.

Cable, who was business secretary for an unusually long period between 2010 and 2015, told the inquiry into the scandal that he never learned who lead campaigner Sir Alan Bates was until just before he left office.

He said none of a group of 140 MPs campaigning on behalf of post office operators came to talk to him about the issues with the Horizon accounting software, adding that “writing polite letters” was not the way to get things done.

In 2015, James Arbuthnot, who tirelessly campaigned on behalf of those wrongly prosecuted, criticised Cable for listening to the Post Office but not the group of MPs and the branch owner-operators affected by what has been described as the UK’s biggest ever miscarriage of justice.

“What is strange about this whole episode is that none of these 140 MPs ever came to talk to me,” Cable told the public hearing on Thursday. “All MPs realise that writing polite letters is not necessarily the way to get through to people in government. You have to talk to them face to face.”

Jason Beer, counsel for the inquiry, asked whether he was blaming the campaigning MPs for not making more effort to see him in person.

“I am not blaming them,” said Cable, who said he only began to “smell a rat” in March 2015, just before parliament was dissolved. “It is not a question of blame. Let’s just say it was unfortunate I never had any personal contact with the MPs about this matter.”

Beer asked whether it really would have been any different if they had, given government officials and the Post Office had managed to maintain a line that there was no issue with Horizon across his time in post.

“Probably, there would have been [a different outcome],” Cable replied. “I would have realised much earlier than March 2015 that serious problems were not being properly addressed by the Post Office and the department and would have started to interrogate it much more aggressively, as I did on quite a lot of other issues when MPs came to see me.”

Cable said he agreed with a description of Post Office management as “thugs in suits” and had a goal of rebalancing the relationship between management and branch owner-operators during his time in office.

He recounted a story about challenging eight branch closures in his constituency, before he entered government, and being treated poorly by the organisation’s “middle management”.

“Mr Bates has, I believe, described them as ‘thugs in suits’ and I recognise the description,” said Cable in his witness statement. “And [the Post Office] dealt with us in an arrogant way when we campaigned against closures.”

Despite a desire to rebalance the relationship between the organisation and branch operators, the issue of the faulty Horizon IT system, which resulted in more than 700 owner-operators being prosecuted between 1999 and 2015 for theft, fraud and false accounting by the Post Office, was rarely ever raised with him.

“Problems with Horizon barely came across my desk,” he said. “When they did, it was usually in a very uncontroversial way and not drawn to my attention as an issue I should focus on. General reason is that the officials who were briefing me and ministers on the subject hadn’t seen it as a particular problem.”

Cable admitted that he should have been more thoroughly briefed on the Horizon system at the time.

“In hindsight, I should have been told at the outset what Horizon was,” he said. “That competent people … were suggesting there was a risk factor, and I should have been told about Mr Bates and the justice group. I never heard his name until I’d been in the job five years. I wasn’t briefed on them.”