I am an EU citizen and I'm currently searching for a job in the UK. I've been working with different agencies over the internet and one of them is asking for my passport (I assume, to verify my identity). The others still didn't but that may entirely because I'm not so far in the job search process with them. The passport is being asked before sending my CV to the actual clients.
Is this acceptable? I do understand what they're after, but I cannot but feel a bit worried about sending a copy of my passport to someone that for all purposes I do not actually know that well.
Question Update
As per Codingo's suggestion, I told them I wasn't really comfortable about it and they told me they were cool with it, but that if my recruiting process with any of its clients comes to fruition I will have to eventually down the road provide the passport, which is something that I'm ok with.