The founders of GLG - the Israeli-American Noam Gottesman and the Belgian Pierre Lagrange - are telling investors not to count on Mr Jabre's return no matter what the outcome of the Financial Services Authority inquiry.
The City watchdog is examining whether Mr Jabre traded in the Japanese company Sumitomo on inside information gleaned from the Goldman Sachs banker John Rustum.
Separately, French financial regulators are looking into Mr Jabre's trading in the French company Alcatel.
The FSA's decision on Mr Jabre is expected soon, while the French are unlikely to arrive at findings for some time. Theirs is the more complex case.
Should the FSA find against him, Mr Jabre faces suspension or even an outright ban from trading. He and GLG will have 28 days to appeal. Such cases are heard again from scratch, and in public.
Mr Jabre officially has taken a leave of absence while his leg, injured after slipping on ice and requiring the insertion of metal pins, recovers. The start of that leave period roughly coincided with Mr Jabre's appearance before the FSA's Regulatory Decisions Committee last month. He stepped down as a director of GLG at around the same time.
One source familiar with the situation said: "The message from GLG to investors is that he [Mr Jabre] is not coming back. He's out for good."
Lebanon-born Mr Jabre, 45, can be counted among the single most powerful traders in London.He directly managed about $5bn for GLG across five funds. Industry watchers have described his investment style as "extremely aggressive".
Under his stewardship, GLG funds have delivered annual returns of up to 30 per cent since he joined in 1997. However, the bonus structure at GLG is thought to have fuelled tension between Mr Jabre and his two partners, Messrs Gottesman and Lagrange. Though Mr Jabre's performance has been less stellar over the past couple of years, he is believed to think he merited a larger slice of the bonus cake than he received.
Bonuses were divvied up equally between the three partners after costs were paid from net profits.
Mr Jabre had just seven (albeit better paid) employees under him, while the other two partners ran larger, more expensive departments of between 28 and 35 people.
GLG, it is said, has hired a dozen people to replace Mr Jabre across its funds.
Mr Jabre has reportedly amassed a £200m personal fortune. He owns a townhouse in the affluent Boltons area of Kensington, west London, and a chalet in the French ski resort of Courchevel.
About half of his net worth is invested in the GLG funds he ran.