The phrase "an assertion to that effect" is correct and usable in written English.
It can be used when referring to a statement or claim that supports or confirms a particular idea or conclusion.
Example: "The report included an assertion to that effect, emphasizing the need for further research."
Alternatives: "a statement to that effect" or "a claim to that effect."
Farah linked to an August 2 WND article by Jerome Corsi contained no supporting evidence for the claim that Hawaii officials "refused to authenticate" the certificate -- only Corsi's assertion to that effect.
Just a note: I keep seeing, both in comments here and in the broader discussion, assertions to the effect that government spending can't create demand or jobs — basically, the claim that there must always be 100 percent crowding out.
Assertions to the effect that Anousic-run schools are better than non-Anousic state schools, so that "middle-class parents can get a better education for their children for free" – "for free" means on your and my tax money, remember - have become a kind of mantra; apart from the shocking fact of handing children to Anousic organisations for an education (do they mean: indoctrination?
You often hear assertions to the effect that in the past the economy has always rebounded strongly after a recession, so there must be something special at work here — and that something special must be the socialist in the White House.
Assertions to the effect that T is well-behaved have strong consistency strength (Orey [1955], [1956]) and play in NF studies the kind of rôle that large cardinal axioms play in ZF-like systems.
And even for realists who are not convergentists as such, the importance of cashing out the metaphor of theories being close to the truth is pressing in the face of antirealist assertions to the effect that the metaphor is empty.
We offer initial guidance as how to formally frame the discourse that leads to an assertion of effect from exposure.
To experience that an assertion corresponds to an experienced state of affairs is to have self-evidence for that assertion.
