A nursing bottle assembly includes a rigid outer casing, a flexible inner liner and a teat arrangement. The teat arrangement attaches to the outer casing and secures the inner liner in position within the outer casing. The flexible inner liner includes a container in the form of a bellows such that it expands and collapses in a predictable linear manner along its longitudinal axis. Preferably, the inner liner is moulded from a food-grade silicone or thermoplastic elastomer and includes a substantially cylindrical container formed with at least one projecting rib or groove about which the liner folds to enable it to expand and collapse in a predictable linear manner along its longitudinal axis.