Royal & SunAlliance (R&SA) is trying to "wriggle out" of paying compensation to dying asbestos victims, the High Court has heard.
Administrators for Turner & Newall (T&N), once the UK's biggest asbestos producer, have alleged R&SA was liable for T&N's asbestos liabilities.
R&SA insured T&N between 1969 and 1977.
However, R&SA is expected to claim it excluded asbestosis from T&N's policies.
It is likely to challenge T&N's disclosure of its risks.
The case started in the High Court on Monday and was expected to run for at least nine days.
On Monday the administrator's QC Colin Edelman accused R&SA of attempting to wriggle out of paying millions of pounds to the 700 UK residents seeking compensation.
No employees have received any compensation since T&N, bought by US firm Federal Mogul five years ago, went into administration last year.
R&SA said it had a "great deal" of sympathy of the employees affected but refused to comment further.