A shareholder vote on Woodside Petroleum’s plan to buy back $US2.7 billion worth of shares from Royal Dutch Shell looks likely to go down to the wire.

Shareholders are due to vote on the plan at a meeting in Perth tomorrow.

But based on proxies lodged ahead of the meeting, Woodside could just fall short of receiving the 75 per cent of votes supporting the deal it needs to proceed with the buyback.

Woodside says vote results so far indicate 71.3 per cent of eligible proxy and direct votes cast are in favour of the buyback, with 28.7 per cent against.

“The general meeting will provide shareholders with the opportunity to vote in person in order to determine a final outcome,” Woodside said in a statement today.

The Australian Shareholders Association has said it would vote undirected proxies in favour of the buyback at Friday’s meeting.

However, the Australian Financial Review reports that junior shareholder Plato Investment Management and some large pension funds oppose the buyback.

Shell, which is Woodside’s largest shareholder, announced in June it would sell 19 per cent of its $6.3 billion stake in Australia’s largest oil and gas producer.

The desire to split is mutual, with Woodside keen to remove the overhang that has capped its share price for years and Shell in the middle of a $15 billion global asset sale, including Australian refineries and service stations.

Woodside plans to buy back 78.3 million of its shares – or 9.5 per cent of the company – from Shell for $US2.7 billion ($A2.9 billion) or $A36.49 a share, if shareholders back the deal.

Another 78.3 million shares will be sold to institutional investors at $A41.35 per share.

Shell will be left with a 4.5 per cent stake.

Former treasurer Peter Costello blocked Shell’s attempted $A10 billion takeover of Woodside in 2001 on national interest grounds – one of only two such rejections in Australia.