(Reuters) — Britain's biggest insurers will be exempt from having their most important indicator of financial health externally audited under proposals issued by the Bank of England on Friday.

New European Union rules will require British-based insurance firms from January to meet a minimum solvency capital requirement, or SCR, to show they have enough funds to meet policyholder commitments.

However, the Bank of England's Prudential Regulation Authority, in a consultation paper released on Friday, said big firms that use their own models for calculating the SCR would be exempt.

That means firms like Prudential P.L.C., Aviva P.L.C. and the Lloyd's of London insurance market would not need to have their actual SCR audited, only information used to calculate it.

Insurers that don't use internal models — but use a standard calculation method set out under the E.U. rules instead — would have their SCR figure audited as well.

"It is the PRA's view that external audit can underpin confidence in the audited information," the consultation paper said.

Markets are already putting pressure on insurers to have an SCR of well above the 100% minimum capital to requirements as it becomes the core gauge of health.

Analysts said the twin-track approach of allowing some insurers to be partially exempt could create problems.

"This would mean there is inconsistency between firms," said Stuart Wilson, an insurance partner at EY consultancy.

While models are vetted by regulators, that does not mean they have been used correctly when calculating the SCR, Mr. Wilson added.

The E.U.'s insurance watchdog, the European Insurance and Occupational Pensions Authority, said in July that external audit can be a powerful tool to ensure high quality of public information on Solvency II.

Wilson said E.U. states were putting EIOPA's guidance into practice, but Britain appeared to the only one so far that has made a distinction according to internal model use.

Audits beyond annual financial reports could include banks as well.

In February, the PRA proposed that accountants for the biggest U.K.-headquartered deposit-taking banks provide written reports to the supervisor annually on financial reporting and the accompanying audit.

Bank of England’s deputy governor and chief executive of the PRA, Andrew Bailey, said on Thursday that banks must be aware that the regulator will "have a line of contact" with accountants that does not go through the lenders.

The Bank of England is due to publish a final policy statement on the February consultation paper in coming weeks.