'foremost motive' is correct and usable in written English.
You can use it to refer to a primary or main reason for a particular action. For example, "His foremost motive for starting the business was to have more control over his future."
Foremost among them is the motive of care, exhibited by women who have been charged with the role of raising children.
He said Ms. Berman's family connection to organized crime was being explored in the hunt for a motive but was not foremost in the minds of the police.
When we asked the JetBlue Chairman what his criterion were for investing he said that, while funding great people has to be any investor's top motive, he unilaterally ranks leadership foremost when evaluating deals.
First and foremost, "Moore's exploration of the [often sexual] motives for costumed crimefighting sheds a disturbing light on past superhero stories, and forces the reader to reevaluate to revision every superhero in terms of Moore's kenosis his emptying out of the tradition".
Children must never be in danger being led and facilitated by any who would have any other motive than the children's best interest as their foremost objective.
A third motive is the challenge (and perverse pleasure) of tackling the pitfalls, foremost of which is research.
He said: "There are one or two in the Remain camp, their spin doctor [Will Straw] being foremost among them, but also some of their speakers, who have tried to say that the motives of that man were somehow whipped up or inspired by a leave campaign that had fought on a nasty, negative and hateful agenda.
First and foremost: Really?
Children first and foremost.
