General Motors has agreed a deal with unions to close its Opel plant in Antwerp, removing an obstacle to completing long-running talks on the restructuring of its European arm.

On Sunday, GM’s Belgian unions agreed to put a buy-out plan to a vote, due to take place this week.

The vote will provide a face-saving exit for the unions, which had vociferously protested against the plant closure, but also faced criticism from some members for failing to agree terms of the buy-out sooner.

The “social plan” which unions agreed to put to their membership is a mix of early retirement packages for workers aged 50 and over, and individual pay-outs that could reach as much as €144,000 ($194,000), depending on seniority, pay and age.

Rudi Kennes, a union leader, said that he was “presenting the agreement, but not standing behind it”. He said: “We cannot share more than there is in the pot.”

Unions had been hoping for a more generous final pay-out in line with a round of redundancies in 2007.

GM said that it expected about half of the plant’s workers to accept the plan. “It is our expectation that about 1,250 of the total 2,600 employees would likely accept the offer quickly and leave the company by the end of June,” GM said.

The US carmaker said that it would then begin a formal search with its unions and the government for an investor for the plant.

While GM is unlikely to find another carmaker willing to build vehicles in Antwerp, it has also spoken to potential investors from outside the industry.

If it fails to find an investor by September, the factory will be closed and the remaining workers given the same buy-out terms as their colleagues.

Belgian law requires foreign companies seeking to close plants to engage in detailed consultations with employees and explore alternatives to a shutdown.

The closure of the plant is one of just two to be announced in Europe since the beginning of the downturn. Fiat plans to close its plant in Termini Imerese, Sicily, later this year.

Once the Antwerp plant’s future is resolved, GM can begin discussions on an agreement to secure €265m of labour cost savings from its European workforce.

GM’s Germany-headquartered European works council had been pushing for an equity stake in exchange for the cost savings.

However, its Detroit-based management has cooled to the idea. GM is now discussing a scheme that would see the cost savings linked to investment guarantees made by the US carmaker.

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