The Supreme Court has begun hearing an age discrimination case brought by a former equity partner who claims his law firm acted unlawfully in making him retire aged 65.

The hearing is expected to last three days from today and the ruling could have wide-ranging implications for how firms may legitimately require equity partners to step aside for business planning reasons.

Leslie Seldon, a former civil litigation equity partner at Kent firm Clarkson Wright & Jakes (CWJ), argued at a 2008 employment tribunal, a 2009 employment appeal tribunal and the Court of Appeal in 2010 that the default retirement age (now abolished) applied to employees only, and not to equity partners who are effectively self-employed.

Seldon was unsuccessful in all three applications. The three courts accepted CWJ’s argument that it retired partners at 65 ‘as a legitimate business aim’ so that younger solicitors at the firm were able to take up their places in the partnership, helping retain talented lawyers who might otherwise move elsewhere to gain promotion. It was, the courts ruled, ‘a proportionate means of achieving a legitimate aim’.

Employment partner Clive Howard at national firm Russell Jones & Walker, who is attending the hearing as an observer, said: ‘The significance of any judicial decision arising from this hearing will be restricted to partners because employees were at that time still subject to a statutory default retirement age of 65. That default retirement age has now gone and employees and partners are now in the same position. Organisations can still decide whether to implement a compulsory retirement age, but they should be cautious - and just how cautious will depend on the decision of the Supreme Court.’

Howard added that it would be a mistake to use a compulsory retirement age in place of a procedure to measure an ageing partner’s performance. He said: ‘That really is lazy management. Organisations should follow fair performance procedures - for young and old.’

Employment partner Emma Bartlett at City firm Speechly Bircham said: ‘The government’s attitude to retirement has changed since Seldon was at the Court of Appeal. It no longer considers it necessary to give employers freedom to retire employees at 65 without justification. The Supreme Court may therefore find it difficult to construe CWJ’s aims to be in line with social policy.

‘Other cases have maintained that workplace planning can be a relevant justification for enforced retirement, and in Seldon’s case he had a partnership agreement under which retirement at 65 was specified. But whether the Supreme Court will accept that these alone are sufficient to justify the inevitable discrimination arising from his enforced retirement is questionable.’

The Equality and Human Rights Commission is supporting Seldon and the secretary of state for Business, Innovation and Skills has intervened in support of CWJ. Supreme Court justices Lords Hope, Hale, Brown, Mance and Kerr are hearing the case.