The company will also have to pay £125,000 costs after being reprimanded by the Personal Investment Authority.
The PIA identified concerns over Britannic's conduct of the review of past pensions mis-selling following a visit to the life insurer in January 1997.
The review relates to cases where people were wrongly advised to opt out of company schemes in favour of personal pensions, mainly during the late 1980s and early 1990s.
Britannic said it had now admitted to a charge that before January 1997, "it failed to take all reasonable steps to carry out its review of past pension transfer and opt-out business in accordance wioth the standards....prescribed by the PIA".
The life insurer said the PIA was now satisfied that it has taken steps to remedy these problems.
Britannic also met the deadline set for completion of 90% of its priority cases by the end of 1997.
The fine is equal to the largest handed out by the regulator over mis-selling.
Last January, the London and Manchester received the same fine for similar reasons.
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