In short:

The Therapeutic Goods Administration (TGA) says 21 sunscreens that share the same base formulation have been recalled, paused or are under its review.

The TGA says it has "significant concerns" about the reliability of SPF testing undertaken by Princeton Consumer Research (PCR), an overseas laboratory many sunscreen brands used to support their SPF claims.

The agency says it has written to PCR about its concerns, but has not received a response.