"ideological rationale" is correct and usable in written English.
You can use it when you want to refer to a set of beliefs or values that help to support an idea or action. For example, "The political party defends its policy decisions with an ideological rationale."
The ideological rationale for workfare is that welfare, of necessity, produces a "culture of dependency".
From the left, voices angrily accuse Mr Field of supplying the coalition with an ideological rationale for slashing financial aid to the poor.
What it will do is give Osborne a new ideological rationale to cut taxes, possibly before a general election in 2015.
The subject is a deeply serious one, of course – an entire industry is in the dock, with good reason – but the po-faced absurdity of the Nazis' ideological rationale would at times make a cat laugh.
In an Administration dominated by businessmen and Western conservatives, he was a prominent intellectual a throwback to foreign-policy mandarins like Dean Acheson, McGeorge Bundy, and Walt Rostow, who provided the ideological rationale for the war in Vietnam.
The time will come when you will be forced to admit not only that the war in Iraq was stupidly conducted, but also doomed to failure from the outset because of the hopeless cultural and political ignorance underlying the false premises of its ideological rationale.
Yet what we do know is that we now inhabit an age in which it's logistically straightforward to commit attacks designed to kill and create mayhem, and there are clear ideological rationales for doing so.
Finally, we contend that a comparative study should analyze cross-country variation also in the argumentative structures – the justifications, arguments and ideological rationales – that surround these policy measures.
— As Gov. Rick Perry of Texas begins his presidential campaign, he is working hard to position himself as the leading Republican champion of states' rights, using his high-profile battles with Washington and his book on the dangers of federal power to build an ideological and constitutional rationale for his fierce anti-Obama message.
"Although the carefully choreographed sacrifice of 'donated' children brought direct socioeconomic benefits to tributary groups who supplied them," they continued, "the ritual would unavoidably — whatever its internal ideological and religious rationale, and however complicit the parents or the wider group — have created a climate of fear".
And then there are the ideological, theological and pseudoscientific rationales lawmakers hide behind to justify doing nothing.
