He said it did not feel “particularly fair” that Wales got no additional cash due to spending on HS2 in England.
Trains in Wales can be “pretty dreadful” and “the maintenance of some of the carts needs doing” he added.
GWR said: “The construction of HS2 and Old Oak Common are flagship projects for the future of the UK’s railway network, but not all of that work can be done without impacting train passengers.
“Our focus is on minimising the impact on passengers and we’ve worked with HS2, Network Rail and the Department for Transport to develop alternative routes and services so they can still get to where they need to go.”