We appear to have a new phenomenon in the newspaper world - the exclusive spawned by the lip-reader.

Lip-readers were, of course, used extensively during the royal wedding to work out what was being said at the altar, although different newspapers came up with different interpretations.

Today, we have revelations of an unseemly spat between David Cameron and Nick Clegg.

They are said to have had an embarrassing argument over NHS reforms during Barack Obama's visit to Parliament last week.

When Mr Clegg appeared to criticise Health Secretary Andrew Lansley, the Prime Minister, is said to have snapped: "It's nothing to do with him NOW!"

How do we know all of this? Because the Mail on Sunday employed a lip reader to monitor the two men as they waited for the President in Westminster.

So, with the debate about privacy laws on the internet reaching fever pitch, we now have a new question: Can't people have a private conversation without wondering if they're being watched by a lip-reader from a national tabloid?

It conjures up some interesting questions for the Press Complaints Commission. Is the use of a lip-reader legitimate? And what if there's a dispute over what was said and there's no actual evidence recorded, other than the testimony of a lip reader?

A secret recording is one thing, but a secret lip-reading is quite another thing.

If newspapers can produce different versions of what was said at the royal wedding altar, they can surely misinterpret what was being whispered by two politicians.