Contributions to the Solicitors Indemnity Fund (SIF) may rise by 30 per cent following the discovery that previous contributions have been underestimated to the tune of £248m.

The SIF admitted last week that it had failed to collect sufficient contributions from members over the past seven years, leaving it with a huge deficit.

The admission follows hard on the heels of two other SIF blunders revealed last year. In one a computer error meant that too much money was collected and then the SIF admitted it had miscalculated last year's contributions and had to levy a supplementary contribution on Law Society members.

The SIF will again be asking solicitors to make up the shortfall through increased contributions. One option likely to be put to council is an increase of about 30 per cent in contributions, which would then have to be maintained for a five-year period.

For a five-to-six partner firm this would mean a rise in contributions of £7,900 from £26,400 to £34,300.

Chair Andrew Kennedy said SIF faced insolvency if council members did not approve the increase.

He said: “The profession knows that it must pay. It's just a question of when.”

Kennedy announced the creation of a review committee to investigate how the contributions were miscalculated on such a grand scale and why the discrepancy was not spotted sooner.

The members, chair David Ward, Paul Venton, Graham White and Ray Treen, are all on the board of directors of SIF.

The SIF said the level of claims for dishonesty, particularly in conveyancing, for the years in question was “disturbing” and went “some way to explaining the contribution deficiency”.

The SIF, which is responsible for advising the Law Society on how much money must be raised each year, has pledged to produce a full report for the society's standards and guidance committee before June, when next year's contributions are to be set.

Copies of the latest audited accounts will be sent to all firms and Law Society council members in the next few weeks and the issue will be debated by council on 6 March.

The Law Society already has a working party considering the future of professional indemnity insurance and this latest admission will further fuel the debate on whether it should switch from a mutual fund to a system of authorised insurers.