UPDATE 1-Centrica makes $2 bln bid for Venture, ups stake

* Centrica lifts Venture stake to 29 percent

* Centrica bid values Venture at 1.3 billion pounds

* Offer will not be increased unless rival bidder emerges

(Adds detail and background)

By Tom Bergin

LONDON, July 10 (Reuters) - Britain's largest gas retailer, Centrica Plc (CNA.L), which operates under the British Gas brand, made a $2 billion bid for North Sea gas producer Venture Production Plc (VPC.L) on Friday as it seeks to increase its gas reserves.

Centrica said in a statement it increased its holding in Venture to 29 percent from 23.6 percent with the acquisition of a stake owned by private equity group 3i Group Plc (III.L).

The company has offered to buy the rest of Venture for 845 pence a share, valuing the oil and gas explorer at around 1.3 billion pounds ($2.11 billion).

Venture's shares closed at 785 pence on Friday.