Is there a function which eliminates spaces?

In a WHERE clause, I want to to compare strings ignoring the spaces
inside them. Is there a function to do that? I do not find it in the
documentation.

SELECT (...) WHERE (ignore_spaces(table.phone_number) ~* igore_spaces(?));

would be fine but ignore_space() does not exist!

Maybe there is a solution based on regular expression, but I do not see it.