"pretend ignorance" is a correct and usable phrase in written English.
You can use it when someone implies that you should pretend to not know something, or that you should feign ignorance about a certain topic. For example: "My boss asked me to pretend ignorance when he called the customer to apologize."
I want a loving relationship, but my feelings are so hurt I don't know if I can pretend ignorance.
After summoning the chiefs of Gaul, Caesar thought proper to pretend ignorance of the things which he had discovered; and having conciliated and confirmed their minds, and ordered some cavalry to be raised, resolved to make war against the Germans.
I thought I would be doing a terrible thing to pretend ignorance.' Then I sprang my carefully prepared trap: 'If you truly believed that there was a Communist conspiracy that presented a real danger to our country, why did you stop there?
When the projects failure is finally made public, he can pretend ignorance.
Bush's strategy, like that of Ken Lay, is to talk a good game and pretend ignorance.
Due to the stigma associated with the condition, many people in rural communities might pretend ignorance of the condition.
Many broke tools, slowed the work pace, pretended ignorance, and in some cases, engaged in violence against their masters.
Hayward, "... like all worldlings raised a little in life, received us very coolly, and pretended ignorance of our affairs".
Recognising each other as adversaries, Bond and Largo begin a tense cat-and-mouse game of attempting to get the drop on each other while still pretending ignorance of their adversary's true nature.
At least we can all feign ignorance and pretend the aliases are different people, rather than one, insanely talented producer.
When the consultant, Aaronovitch, returned and proposed to take her into his confidence, she pretended complete ignorance — to protect the student doctor and to hear the fullest possible account of her illness.
