"The recruiter I'm working with said they won't accept the application unless I provide my current base salary."
OMG. WTF. 'K Off!
You could perhaps:
- tell them that your current salary is sensitive company information and your contract of employment states that you may not disclose sensitive company information to competitors
- tell them that your current salary is sensitive personal information and, with reference to the data protection act, you wish to disclose it to them no more than you might wish to disclose which brand of hemorrhoid cream you use
- tell them that you can see through their pathetic negotiating gambit and that you refuse to be anchored down by your current salary, bearing in mind in particular that the reason you're moving on is probably because you feel under-paid in your current role anyway
- tell them to stop being so damn lazy and to interview you properly to see whether you're "worth" a certain amount, rather than relying on what you're being paid at present as a benchmark
- tell them that your expectation is for a salary of around £X-Y. Then, when they ask what your current salary is, tell them that your expectation is for a salary of around £X-Y. Repeat ad-infinitum.
All of the above options however are unnecessary, given that they will inevitably lead to you not joining the firm anyhow. So, the two following options may be preferable:
- suck it up and possibly end up joining the firm knowing that you probably got slightly shafted on the salary front and that you're probably never really going to be completely satisfied with what you get in return for all that hard, hard work and all those late, late nights
- apply elsewhere and don't bother responding to their calls.