It is estimated that half of all emails are spam, and a decent chunk of those are pornographic.

So it was timely that MPs held the UK Spam Summit this week, with a range of experts and government officials from Europe and the US discussing the issue.

What became clear listening to them is that, while everyone agrees that spam is a problem that should be tackled, there is broad disagreement on how to go about this.

In the US, they are pushing an opt-out model, where the receiver must email and ask the sender to stop sending them junk email. In Europe, we are looking at opt-in, where marketing material cannot be sent unless we give permission.

So, the US believes that serial spammers will stop if we send them a polite email saying that we no longer need information about Viagra or penis extensions. Am I the only person who finds this quaint view of spammers terribly naive?

Surely the only purpose served by demanding that you no longer get such emails is to confirm your address, thus ensuring that you receive even more spam.

So what about the European approach? It sounds far better, but again relies on the honesty of spammers not to abuse your email account or flout the law by sending unsolicited emails.

Worse, if we are opt-in and the US (and potentially other countries) are opt-out, what is to stop a serial spammer setting up in a country where they can flood you with mail until you request that they stop, which they can then ignore if their servers are based in a country with weak laws?

Spam is a global problem which requires a global approach and a global solution. Ideas such as charging a small fee to send email, thus making bulk email less attractive, or mandating the use of filters by ISPs have been dismissed.

Nor will automatically returning all spam to the sender work; it would overload ISPs' mail servers and the spammer may have hijacked a legitimate company's server to distribute the mail.

So, if legislation is the approach, it needs one law around the world to which different governments subscribe and which closes the loopholes that spammers can abuse.

Also, governments must have the political will to tackle the problem. This means that legislation needs to pay more than lip service to the issue. Don't tell us that abusers will be fined - prove it.

Governments need to join up with industry and jointly fund the police (or the body tasked with tracking spammers down) so that they can investigate abusers - some of whom will be sending out unsavoury material, others illegal - then take them to court and hand out sentences that hurt.

Otherwise, email will continue to be stifled by unsolicited, bulk messages that clog up servers, offend some and annoy many.