Sneaky PC users who've been watching Jeremy Paxman for free on their PCs via the BBC's website need to buy themselves a TV licence, according to the licensing authority, writes Chris Ward-Johnson.

The advent of broadband xDSL and cable modem services means more and more people will be tuning in on their computer screens instead of watching on their tellies.

And, it seems, the licensing authorities have already thought about this one and are advising anyone who asks that yes, you do need to buy a full TV licence if you're tuning in on your PC.

"...a television licence is required if you use television receiving equipment to record and/or receive certain television programme services," says Anthony Hardwell, Policy Manager of the Post Office Policy Group. "This means a licence is needed to receive BBC, ITV, Channels 4 and 5, digital television, other terrestrial services, satellite television (from a place in the United Kingdom) and cable television."

So far, so reasonable - if you have a telly, you need a licence.

However, Mr Hardwell goes on: "With this in mind it does not matter how the service is received but whether or not it is."

I had asked the TV licensing authority for clarification of this point after being asked the question by one of the users of my technical help website at www.drkeyboard.com/chat. At first, their replies were a little unclear referring to 'computers with the facility to receive TV programmes' which seemed to mean just tallies with a tuner card.

But now, adds the Post Office's Michael Collins of their Customer Services department, "If your computer is capable of receiving live broadcasts, whether on-line, through an aerial or satellite dish, then it is classed as television receiving equipment..." You're OK if you already have a TV licence, but what about companies where staff are ogling Paxperson online?

"Your point concerning all on-line users requiring a licence maybe incorrect as a licence is only required if individuals use their PCs to receive programme services (i.e. Newsnight)," replied Mr Hardwell. "If (even though they have the capability) the individual chooses never to access such programme services a licence will not be necessary."

And, just in case you were wondering how on earth they'll know you're watching the news online, Mr Hardwell adds, "Finally our detection equipment is capable of picking up television reception via computer. And no, the BBC do not look at IP addresses for licence fee evasion."

It's my understanding that TV detector vans work by picking up the radiation emitted by cathode ray tube TVs - which should mean that, if you're rich enough to run an LCD monitor they'll never know you're a secret Paxman admirer.

Newsnight is shown, live, on the BBC website every weekday night at www.bbc.co.uk/newsnight.