We have a cat flap in our garage so that my two cats can come in (though they usually sit and whine at the front door because they're too lazy to come in the cat flap ) and just recently, a new cat has moved into our street and it comes into our garage. My youngest cat is terrified of this cat and for hours after won't come inside and stands at the garage door looking in for ages. I've come home before and seen this other cat sat in our garage, and my cat is outside too scared to go in. My dad scares the cat off, but still for ages my cat won't come in. He gets really freaked out and I was just wondering if there's anything I can do about this?

Have your cats microchipped, if they're not already, and get a microchip cat flap. They are the most discriminating type of cat flap for only letting your own cat in. Continue to chase off the other cat whenever you see it. Water pistols or a hose can be useful to get rid of it without hurting it or scaring your own cat by making a lot of noise.

Good advice.
We have 3 cats & our neighbour has just the 1 but had a cat flap then realised our cats was also using it to come in & torment her cat She solved the problem by getting one of those microchip cat flaps. Think our cats have given up going round there now to try & get in.

Ok, thanks for the replies

The microchip cat flap is the best advice that I can give too. We had the same problem of a big white cat coming in and scaring my cats and also eating their food. Got the cat flap and all that has changed. We don't have any problems anymore and my cats are the only ones that can use the flap. TBH it is the best invention that I have ever come across and it has changed mine and my cats lives tremendously.

Thanks Zigesa