Fibre plants favour different growth conditions and require different levels of husbandry. However, the fibres share some physical and material properties, which make them difficult to distinguish in the archaeological record. This thesis evaluates the effectiveness of methods for characterising bast fibres including; fibre chemical analysis, mechanical testing and fibre morphology, to propose that longitudinal microfibrillar angle (MFA) and cross-sectional circularity (Ct) used in a two-step procedure to analyse selected modern fibres of nettle (Urtica dioica L.), flax (Linum usitatissimum L.) and hemp (Cannabis sativa L.) could offer an alternative approach. The reliability of MFA and Ct, as diagnostic features, was evaluated under a temperature accelerated degradation 48week trial with eight fibre types from three deposition soils Post deposition, surviving fibres were subjected to evaluation of changes in MFA and Ct. An additional check on the diagnostic efficacy was conducted within a blind-test protocol. Finally, the research programme employs MFA and Ct in the diagnosis of a range of archaeological textile fibres from museum collections and fibres from the Kasr el Yahud mass burial. The thesis includes recommendations to address future post thesis research programmes.