Several certificateless short signature and multisignature schemes based on traditional public key infrastructure (PKI) or identity-based cryptosystem (IBC) have been proposed in the literature; however, no certificateless short sequential (or serial) multisignature (CL-SSMS) or short broadcast (or parallel) multisignature (CL-SBMS) schemes have been proposed. In this paper, we propose two such new CL-SSMS and CL-SBMS schemes based on elliptic curve bilinear pairing. Like any certificateless public key cryptosystem (CL-PKC), the proposed schemes are free from the public key certificate management burden and the private key escrow problem as found in PKI- and IBC-based cryptosystems, respectively. In addition, the requirements of the expected security level and the fixed length signature with constant verification time have been achieved in our schemes. The schemes are communication efficient as the length of the multisignature is equivalent to a single elliptic curve point and thus become the shortest possible multisignature scheme. The proposed schemes are then suitable for communication systems having resource constrained devices such as PDAs, mobile phones, RFID chips, and sensors where the communication bandwidth, battery life, computing power and storage space are limited.