The row that has suddenly blown up between barristers and solicitors over the standard of the latter's advocacy in family cases lacks one crucial element - evidence.

The Bar Council and Family Law Bar Association are agitating for the government to commission a review like Sir Bill Jeffrey carried out in relation to criminal law advocacy.

But the letter they sent to justice minister Shailesh Vara requesting it contains nothing more than anecdotal evidence, and even that is vague. Maybe they are hoping to ride the wave of Lord Chancellor Michael Gove's professed desire to protect the independent criminal Bar.

Sir Bill's review, of course, came off the back of all the work and arguments around the introduction of the Quality Assurance Scheme for Advocates. QASA dates back to the 2006 Carter report, in which Lord Carter said that market forces alone can no longer be relied upon to eliminate under-performing advocates.

Other evidence then emerged in the following years that led to the start of the QASA process and then the Jeffrey review.

That evidence was piecemeal, but there was enough to point to a problem that needed investigating.

So far as I am aware, not even this relatively low level of evidence exists in relation to family law advocacy.

As the essence of the argument is that the interests of clients and justice are best served by being represented in court by barristers rather than solicitors, the Bar is always going to be open to the charge of self-interest. Similar arguments have been had in crime around the growth of higher court advocates in solicitors' firms, and the CPS's use of associate prosecutors.

But if they want to make their allegations stick, barristers have to come up with some proper evidence.