The phrase "additional doubt" is correct and usable in written English.
It can be used when referring to extra uncertainty or skepticism regarding a particular issue or situation.
Example: "After reviewing the evidence, I still have additional doubt about the validity of the claims made."
Alternatives: "further uncertainty" or "extra skepticism".
The findings cast additional doubt on the heavily delayed scheme, which faces severe difficulties.
The studies cast additional doubt on the effectiveness of an approach to fighting heart disease that was once perceived to hold great promise and is still pursued by other pharmaceutical companies.
Even so, the exercise would cast additional doubt over Britain's global posture and offend old allies.It already has—as witnessed by Britain's no-show in a Franco-German effort to make peace in Ukraine.
Another e-mail indicates that the pension official's brother received a favorable "discount" on the film deal, casting additional doubt, among investigators, on Mr. Rattner's claim that the arrangement was commercially reasonable.
Further, additional doubt can be cast on EMT and EndMT data due to recent reports which demonstrate that Cre drivers previously thought to exclusively label epithelial or endothelial lineages (for example, Tie2) do not possess the necessary specificity to conclude that progeny labeled by these markers are exclusively derived from the epithelium or endothelium [ 41].
François Baroin, the French finance minister, and Didier Reynders, his Belgian counterpart, acted on fears that the problems at Dexia might lead to contagion elsewhere in the financial system and raise additional doubts about other European lenders.
"Whether we are incompetent or not, I'll leave up to you to judge," he told lawmakers at a scheduled hearing that turned into an accounting for the turmoil after the announcement, which frightened savers by proposing to tax their deposits and raised additional doubts about the viability of the euro currency.
The absence of comparative studies might also cast some additional doubts on the methodology followed, which is the reason why cross-country studies using a common methodology can contribute to test the appropriateness of the standard of living approach.
Subsequent tests raised additional doubts about the product's ability to withstand fire.
But they do cast additional doubts on Rhee's efforts to accentuate the similarities between her politics and those of the unions she's often fought.
That the election remained a squeaker despite Romney's distinct spending advantage over his nearest competitor, former Sen. Rick Santorum, raised additional doubts about his ability to connect with voters.
