Canada's Denison Mines has let its takeover offer for uranium explorer OmegaCorp expire after a London-based company trumped it with a rival offer bolstered by pre-bid acceptances of about 20 per cent.

The bid leaves Denison in the unenviable position of holding 31.5 per cent of OmegaCorp as a result of its cash offer. Acceptance of the higher all-scrip bid is its easiest exit strategy.