A Court of Appeal ruling could make defending some claims through the courts much harder, according to legal experts.
The ruling has also angered insurers, who are calling for parity in the use of witnesses.
The Court of Appeal ruled in the personal injury case, Beck v Ministry of Defence, that in order to call a replacement witness, defendants must disclose details of the first witness.
Lord Justice Simon Brown said it was not appropriate to allow defendants the right to substitute one expert witness for another without disclosing the first report.
Legal experts told Insurance Day that the case highlighted the fact that defendants will in future need a good reason to switch expert witnesses.
Allison Dias, a partner in Davies Arnold Cooper, said it could become more difficult for defendant insurers to instruct their own experts in a bid to save time and money.
An ABI spokesman said: "We are concerned about the levels of costs in legal actions. We want a streamlined legal system and anything which complicates cases doesn't assist with this aim."
