In many occupations it's possible to tell a few porkies within employment applications without anyone bothering about it. I can't help thinking that though anyone applying for a position in the field of legal services should probably steer clear of falling foul of Section 2 of the Fraud Act 2006!
Just tell the truth or, at least, your version of the the truth. e.g. "I'm not too sure as to whether Firm A will provide me with a reference, as I left there after we had a falling out. Firm B will, though, be sure to support my application with a decent reference". Employers (including employment agencies) are often happy to accept one personal reference (e.g. from a friend or former colleague) as long as they've got another reference from an employer to back it up.