No, you should be honest, and if you lie in some material way and he finds out, he should fire your ass, and give you bad references when people call. But to call it criminal is ridiculous.
Isn’t lying on your resume potentially a form of theft? If your resume says fraudulently, i.e., you graduated PBK from your university, and the boss hires you based on that fraudulent information, you’re taking a spot that doesn’t honestly belong to you. Any $ you made while holding that position is a form of theft, and it’s deprived another who might honestly deserve the position of those same $s.
The whole Brit education and employment systems are quite different from the US. Perhaps that accounts for the criminality vs. ‘just’ immorality here.