Venture Production, the North Sea oil and gas company, attempted to strengthen its defence against a £1.3bn ($2.1bn) takeover bid by Centrica on Friday, advising shareholders in a 50-page letter to not sell their shares “on the cheap”.

Centrica, Venture’s largest shareholder with a 29 per cent stake, launched its 845p-per-share final offer on July 10. The offer, which Venture rejected, was at an 8 per cent premium to Venture’s share price at the time. Its shares closed at 839p.