Could it be moths?

Yup! Definitely moths that make these tiny holes in tops. They will only go for cotton or other natural materials, so short of buying all your clothes in polyester not much you can do.

It's not adult moths, it's the larvae.

www.deliciousdays.com/archives/2011/07/11/tiny-holes-in-your-favorite-shirts-kitchen-mistery-solved/
Lots of theories on Google, it seems to be a common problem.

Little devils - I didn't realise it was the larvae though.

Bastards!

they have to lay them somewhere [so they can eat!]

Buy beige crimplene phoenix Nothing goes for that!

Including me, roses

Can you still buy crimplene?

Strangely enough, sunseeker, I was astonished to see crimplene garments in a dress shop, but can't remember which one. I thought it had had its day by the '70s!

I used to have a marvellous yellow crimplene min dress as a teenager [it was my 'pulling' dress]

mini

Could have been worse, roses you could have accidentally added a couple of letters rather than omitting one!

I've taken to keeping my 'best' woollies in ziplock plastic bags. I had found little holes in a not-too-precious cashmere jumper, so didn't want it to happen to really nice ones.

I do find cedar balls etc., very good at keeping the moths at bay - I will probably go and find clothes full of holes now!

There seem to be lots of very tiny moths around indoors at the moment, I had better check the wardrobes.

I had no idea they went for cotton as well as wool.

They go for anything 'natural' roseq wool, cotton , silk etc.I keep my cotton t shirts folded in a drawer, rather than hanging in a wardrobe, but even so , now and then I do still find the holes.The cedar balls are very good though, as is highly scented soap just leave a bar in the drawer or wardrobe.

I will buy some cedar balls, already use scented soap in my wardrobe, but DH just found a moth in his wardrobe on his cotton trousers!

It could be biological washing powder causing the holes. The enzymes can "digest" the fibres. But the care label should have said 'do not use bio detergent'.

[surprise]

If these T shirts are that "knitted" cotton fabric I wonder if it's faults in the cotton, weaknesses in the threads etc. that have broken causing the knitted fabric to come apart.

How long does it take for clothes moths to lay eggs and hatch out cloth eating grubs? Most T shirts get worn and washed very frequently which should kill and grubs. Has it has it happened with any other things you have?

I am with shysal's Posted link on this. Particular the thinner fabric.

Phoenix You do also have cats!

The holes in mine are randomly spread, so the worktop theory doesn't seem to apply. It's definitely not the cats!

I have them too exactly as in the link by shysal. It's very annoying.