"a weak excuse" is a perfectly valid and grammatically correct phrase that can be used in written English.
For example, you might say: "My boss seemed unconvinced by my weak excuse for being late."
That's a weak excuse, a lame excuse".
Later, he added that referring to distractions was to make a weak excuse.
Is that why Abbott's explanation for sending her son private is seen as a weak excuse?
Unions generally blame apathy for student ignorance of their function, but that's seems a weak excuse for poor performance.
That is now a weak excuse for a party with 63 MPs seeking equal status in a three-way election.
"That is a weak excuse for the failures of our school system, our government and our gun laws.
Like most partners, she initially didn't buy into the concept of sex addiction ("it sounded like a pretty weak excuse for an affair") and even when she did start to believe that her husband's behaviour was compulsive, her friends didn't ("they'd look at me in despair, asking since when had sexual desire became a monster that can't be controlled"), leaving her feeling isolated.
She thought that was a pretty weak excuse.
But Mr Liddell-Grainger says: "That's a pretty weak excuse.
Yes, it's a pretty weak excuse, but it's not the worst we've ever heard.
"That's just a feeble excuse to provide weak support for an incredibly evil man.
