So MI5 and the Home Secretary have detained Mike Hancock's Russian researcher and are seeking her deportation. Mike has said that he knows of no evidence of her having undertaken any illicit or illegal activity and has demanded proof if it exists.
I can't comment on the rights or wrongs of the case as I don't know the details. But the BBC has made clear the very low threshold of the sort of information being passed on which might constitute espionage. It appears that even perfectly open source information might count as spying.
If that is the case, then I suspect that there are tens, if not hundreds, of MPs and their staff who are engaged in similar activities.
The job of foreign embassies is to gather information about the country they are based in. Some is gathered from the newspapers, but much comes from contacts - perfectly innocent individuals who pass on their knowledge, none of it secret. I know that there are many MPs who frequently talk to people from embassies. If they talk about (non-secret) information, does that constitute espionage?
There are also many lobbyists, often former MPs, who have House of Commons passes who have clients who are foreign companies or governments. If those lobbyists find out information - even open information - and pass it on to foreign clients, are they not also guilty of espionage?
When I worked for the Electoral Reform Society I talked to many foreign diplomats to provide information on the UK electoral law and voting systems. None was secret (everything could be found in Parliamentary records or text books) but it was nonetheless easier to talk to an expert and get specific answers to specific questions. Was it wrong to talk to diplomats from Germany, Indonesia or China (among others)?
If the BBC is to be believed and the threshold is really that low then we will soon be in the business of having to report any and all contact with foreigners - a truly totalitarian idea.