Sky News has been "rocked" by the defection of political editor David Speers to ABC – and could try to delay his move to the public broadcaster.

Sources close to Speers expect the News Corp-owned channel to assert its contractual rights over their long-serving presenter.

Speers is poised to replace departing Insiders host Barrie Cassidy, who finishes on June 9. But a Sky spokeswoman confirmed Speers remains contracted to the 24-hour channel.

It is believed Speers has a two-year agreement with Sky, expiring at the end of this year, and he may be subject to a "non-compete" clause.