Outspoken: Sir Vince Cable has not gone quiet since losing his seat as an MP

When he was Business Secretary, Sir Vince Cable launched an investigation into the last major High Street collapse – at Comet – and following the BHS debacle he is now calling for Ministers to be given powers to take firmer action against former directors in such cases.

Cable has also been making his voice heard over the question of the EU referendum.

He is a pro-European and he has issued stark warnings of 'messy outcomes' if the result of the vote is not crystal clear one way or the other.

Speaking about BHS, where former boss Sir Philip Green is accused of running it down before its sale last year, Cable says events should not go unchallenged.

'In quite a lot of cases there's a feeling of extreme frustration, that although this isn't fraud it's very, very bad behaviour,' he says. 'The taxpayer is left with a bill and you don't have satisfactory mechanisms for dealing with it.'

Cable's views will be taken seriously because of his involvement with the situation after the collapse of Comet.

Amid suggestions that its private equity owners had walked away with tens of millions of pounds in profit from the administration, Cable launched an investigation.

But the outcome was unsatisfactory, he argues – with a report being produced that involved no action and could not be published.

'It's a peculiar system, governed by legal processes, not done in a very open and democratic way. Even when you had criticism of directors it was difficult for the Secretary of State to wade in.'

He is critical of Green's tenure at BHS, saying the collapse 'reflects very badly on his custody'. Cable adds: 'Morally and ethically he should be making good the deficit in the pension fund.'

The Liberal Democrat lost his Twickenham seat a year ago, but he has not gone quiet.

He has intervened over Tata Steel UK – pointing out the necessity of sorting out its pension problems before a sale could be contemplated – and he has been outspoken on the subject of executive pay.

And Cable has spoken in five debates on the subject of the EU referendum in the last fortnight.

'The scenario not too many people are talking about is a very, very close result on a low turnout, so it has low legitimacy,' he says.

'If there is a 51/49 vote for Brexit on a 50 per cent turnout, Parliament isn't going to allow Brexit on that basis. There could be messy outcomes where the way forward isn't at all clear.'

Despite that he says he is 'reasonably optimistic' that the Remain side will win, but adds that it has not been all plain sailing.

'One has to acknowledge the Brexit campaign has had the best tunes. The idea you are controlling immigration has got through. The Brexit people have had the wind behind them and Cameron and Osborne have had their troubles.'

He has noticed a generation gap among voters. 'With young people the In vote is overwhelmingly strong. For pensioners, Brexit tends to come through,' he says.

There could be messy outcomes where the way forward isn't at all clear - Vince Cable

Cable now has several academic roles, as a professor at the LSE, the University of Nottingham and St Mary's University in Twickenham.

He has written a book – entitled After The Storm – about the financial crisis and he works as a director of several small businesses.

Although he says he is unlikely to stand for office again, he is chairing a new tax policy group for the Liberal Democrats and remains an influential figure on issues concerning the steel industry, executive pay and other matters.

He is backing calls by Shadow Chancellor John McDonnell to implement a crackdown on executive pay by making it a requirement that staff get involved with the process. Cable describes this as a potential 'big game changer'.

At the moment companies only have to report on whether they have consulted staff – and few do.

Cable adds that he would like to see shareholders be more open about what they are doing to control soaraway pay packages.

'One small thing would be to make it an obligation on institutional shareholders to declare how they voted and publish it,' he says.

On the subject of steel, he launches into a surprising defence of European state aid rules. Many say these get in the way of governments trying to prevent the collapse of big employers like Tata Steel UK.

Crisis: Cable has intervened in the Tata Steel sale which has been held up by a pension deficit

The rules – intended to encourage fair competition across the EU – stop governments from subsidising favoured industries.

Cable says: 'Firms come the whole time to tell government to put in money – particularly in the steel industry.

'You would be faced with vast open-ended commitments if you got a bidding war between member states. It is very much in our interest that there's a disciplined system.'

Cable does not want to give too much away about the Liberal Democrats' new tax policy group, but two things interest him.

'We need to shift the burden of tax away from equity on to debt,' he says. That means a possible further crackdown on companies like those in private equity which take on huge loans and deduct the interest costs from their profits to reduce their tax bills.

He adds that he would like to bring back tax relief on capital gains tax, which was abolished by the Coalition.

Cable says the move would encourage long-term investment by allowing people to pay lower CGT if they hold on to an investment.