Fortnum & Mason sent Smith then a private message, saying that there was a "separate reception for Paralympians in the works" which would be announced soon.
The store apologised for the "failure of communication".
The message read: "We are really sorry that we could not do both of the planned parties together, which would have been our preference, but we are restricted on space and simply could not have fitted everyone in at the same time."
But Shaw said the response appeared "reactionary" and "very much reads as an excuse".
"It doesn't seem like it was even thought of until there was a backlash."
He added: "If they had wanted to do an event for us, we would have known about it before. And if they really wanted us there, the venue could have been bigger."
Shaw also said that hosting a separate event at a later date did not take into account the difficulty for many disabled athletes in travelling to London.
"Accessibility is difficult for people with disabilities and it’s just ignorant and upsetting that they even had the thought to do it after.
And in this situation, even if you only have room for a certain number of athletes, why would you not prioritise the ones with accessibility needs?"