It is the sort of thing that gives lawyers a good name. MPs spent three hours last week debating Labour’s call for an ‘independent, forensic, judge-led public inquiry’ into the culture and professional standards of the banking industry.

Gone were the familiar complaints that judges were conservative and out of touch. No longer were we being told that judicial inquiries, staffed by teams of barristers and solicitors, took too long and pulled their punches. Ed Balls, the shadow chancellor, could hardly have been clearer: if an investigation needed powers to compel witnesses to attend and produce documents, it had to be set up under the Inquiries Act 2005.

But that was not on the political agenda. Perhaps still smarting from his questioning last month by Robert Jay QC, Robin to Lord Justice Leveson’s Batman, the prime minister was in no mood to volunteer for more of the same. He must have thought that a committee of MPs and peers, chaired by a Conservative MP and presumably with a built-in coalition majority, would be much more manageable.

We shall see. The committee is to be chaired by Andrew Tyrie MP, chairman of the Treasury select committee, who is far from being a pushover. He made it very clear that he would not take the chair of a committee that was riven by political differences. But will it be thwarted by the legal process? Last Friday, the Serious Fraud Office (SFO) announced that it was launching a formal investigation into attempts to manipulate the level of Libor, a key benchmark interest rate used around the world to help set the price at which households, individuals and businesses can borrow. That seems to mean the SFO will be considering whether it can charge individual traders with fraud.

In the Commons a day earlier, the attorney general Dominic Grieve QC had said that the government’s proposed parliamentary inquiry would have to ‘adapt to any criminal investigation or inquiry that takes place’. In an attempt to explain what this meant, he added the Tyrie inquiry would have to ‘respect comity with any other court or proceedings’.

What the attorney seemed to be suggesting was that Tyrie should not inquire - in public, at least - into any aspect of the Libor affair that might prejudice future criminal proceedings. That must surely make things very tricky for the committee. In the Commons, Balls argued that a judge-led inquiry would be more adept at negotiating pitfalls such as these. That may be so, but Tyrie is likely to have a lawyer at his side to warn him of prejudicial questions whenever the committee is sitting.

How much better it would be if the lawyer was questioning the witnesses on behalf of the committee. These days, it is standard practice for judicial inquiries to appoint their own counsel. The procedure has been carried over to high-profile inquests. Could we now see counsel to a parliamentary committee asking the questions?

This is not something that has been done before, as far as I know. At first sight, it seems inconsistent with the principle that the only people allowed to speak in parliament are members of the Commons or the Lords. But there are exceptions: lawyers used to address the law lords when they were a committee of parliament and witnesses regularly answer questions from committees of MPs or peers. It would be perfectly possibly for parliament to vote the Tyrie inquiry the power to employ its own inquisitor.

Of course, parliamentarians may not want a subsidiary role in questioning witnesses. But recent experience has shown that MPs - differing in their political objectives and competing to impress their constituents - are pretty ineffective at questioning leading business figures such as Bob Diamond and Rupert Murdoch. Even less effective was some of the questioning we saw a couple of years ago from Sir John Chilcot’s inquiry into the Iraq conflict, whose members had decided to do all the interrogating themselves.

That is not to belittle politicians or privy counsellors. Unless you have experience in advocacy or, perhaps, broadcasting, you are unlikely to be skilled in cross-examining witnesses in public. And committees that ask their own questions face two further disadvantages. You cannot really judge the impact of an answer if you are having to think of the next question to ask. And you cannot follow through a detailed line of questioning if you must constantly give way to your colleagues.

Of course, people will not give evidence to Tyrie unless they are promised immunity from prosecution. Witnesses are normally told that their comments are protected by parliamentary privilege. But doubt was cast on that view last month in a report for the Constitution Society by Richard Gordon QC and Amy Street. The two authors also questioned the widely held view that parliamentary committees had coercive powers, enabling them to compel the attendance of witnesses or to punish those who might refuse to answer questions or provide documents. On closer examination, these turn out to be largely empty conventions, unenforceable except in the court of public opinion.

So the Tyrie inquiry needs not only the power to employ its own lawyers: it also needs the power to ensure that those lawyers’ questions are answered. Giving a committee of MPs and peers new powers such as these is not something that can be done overnight, not least because it will set a precedent for future parliamentary inquiries. How fortunate it is, then, that the Commons is planning to start a six-week recess next Tuesday.