Oil and gas explorer Tap Oil has received a second takeover bid — though its board is backing an earlier offer from Singapore shareholder Risco Energy.

A second major shareholder, Northern Gulf — which owns 25.5 per cent of Tap — has today made an unsolicited, off-market offer for another 10 to 20 per cent.

Northern Gulf is offering 10c to 11c a share.

Risco — which owns 28.5 per cent of Tap — last week upped its offer from 7c to 9.1c.

Tap Oil (ASX:TAP) is a Perth-based oil and explorer with offshore projects in the Carnarvon basin of Western Australia and Thailand.

The Northern Gulf offer is conditional on two independent directors withdrawing their support for the Risco bid and backing theirs — which they have so far refused to do.

In January, Risco managed to roll the Tap board and install two of its own people, Chris Newton and Govert van Ek — the Perth cryptocurrency boffin who founded Power Ledger and has a long track record in the oil sector (last seen at Sun Resources – ASX:SUR).

They were joined by Kamarudin bin Baba, Northern Gulf’s in house lawyer.

Risco made its unconditional bid in May.

Risco and Thailand’s Northern Gulf strengthened their hold on the company in 2016 when the debt-riddled producer was forced to overhaul the business as it struggled with low oil prices.

At the time it fended off a board spill by Northern Gulf founder Chatchai Yenbamroong, but disagreements remained about reserves payments and cash calls for the Thai Manora oil venture.

Tap made about $US10.5 million in revenue in July from oil sales from the Manora field.

Tap shares were flat on Friday at 9.1c.

Tap shares over the last 12 months were given a huge boost, not by the ongoing rise in oil prices but by the Risco takeover offer.