it is because, it was because

[joham]

Martin Hewings' ADVANCED GRAMMAR IN USE 2004 edition CD ROM contains such a dialogue (in unit 98):

--Ken was sacked because he disagreed with his boss.
--Actually, it is because he didn't do any work that he was sacked.

I thought 'was' would be better than 'is' here. But is 'is' also a right choice?

Thank you.

[RonBee]

Re:

Actually, it was because he didn't do any work that he was sacked.

That is good. You could also use is there. (I could attempt an explanation, but it is 3 o'clock in the morning as I type this, and I should be in bed. I'll be headed there soon.)

I hope that helps.

~R