A composition for use in the formation of a lignin-based carbon fibre precursor is disclosed. The composition is a blend of a lignin and at least 10wt% of a thermoplastic elastomer. The thermoplastic elastomer may improve the mechanical properties of the lignin-based blend to the extent that conventional carbon fibre precursor formation processes can be carried out using the blend whereas said processes would have been problematic and/or failed when using only lignin to form the carbon fibre precursors. The thermoplastic elastomer is suitably a thermoplastic polyurethane. A carbon fibre precursor produced using the composition is also disclosed, as is a carbon fibre produced from said carbon fibre precursors. Methods of forming said carbon fibre precursors and carbon fibres are also disclosed.