The former Liberal Democrat leader, who had the cabinet role for five years from 2010 to 2015, said there was "clearly a policy failure" under his watch relating to the oversight of Post Office.

That was despite Sir Vince admitting he had been previously aware of "arrogant" management due to past dealings with the company over branch closures in his capacity as an MP.

He agreed with a description of executives, put forward by Horizon IT scandal campaigner Sir Alan Bates, that likened them to "thugs in suits".

But under questioning from counsel to the inquiry Jason Beer KC, he joined other ministers of the era in their respective evidence by insisting he was guided by departmental officials not to interfere in operational matters at the Post Office.

Sir Vince told the probe he "hadn't the faintest idea" the Post Office was privately prosecuting sub-postmasters during his time as secretary of state and declared that problems with Horizon "barely came across my desk".

"When they did", he added, "it was usually in a very uncontroversial way."

More than 700 sub-postmasters were wrongly convicted of charges including theft and false accounting between 1999 and 2015 relating to their use of Horizon accounting systems, provided by Fujitsu, within their branches

While all have been cleared, many are still awaiting compensation.

The inquiry is examining many facets of behaviour over the course of the Horizon life cycle to date.

A central theme is one of cover-ups, not least at the Post Office itself.

In his witness statement to the inquiry, Sir Vince said: "These abuses occurred under a large number of ministers in Labour, coalition and Conservative governments and we all share some responsibility for the fact that this happened on our watch.

"I accept my share of that responsibility and apologise to the victims for the fact that they were so grievously let down.

"I should add that while the focus of the inquiry is quite properly on the sub-postmasters and injury that they have suffered, the dishonesty of Post Office officials has also done harm to trust in official advice without which government cannot properly function."

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In his evidence on Thursday, he added: "To be frank, I found it very difficult to pinpoint particular events or decisions that I could have done differently - but simply, as a matter of formal responsibility, this was a state enterprise that came within the remit of my department and I accept the fact that it happened on our watch.

"I know that's a cliche, but it's something that ministers have to recognise."

Mr Beer asked: "When you say that you accept your share of responsibility, what are you accepting responsibility for?"

Sir Vince replied: "General oversight of the department and this was an area of the department where, clearly, there was a policy failure."