Tony Abbott has said the closure of Alcoa’s Port Henry aluminium smelter was a result of “the carbon tax doing its job”, despite the company having explicitly stated the carbon tax was “not a factor” in its decision to shut.

In a press conference to announce the purchase of new military aircraft, the prime minister said: “We are all mourning the close-down of the Alcoa plant at Port Henry near Geelong, but I regret to say that is the carbon tax doing its job. It’s not the only factor in the closure, don’t get me wrong, but the whole point of the carbon tax is to stop operations like that and under the former government’s own modeling there was going to be a 60% plus reduction in aluminium manufacture here in Australia.

“If you are serious about protecting jobs in manufacturing let’s get rid of the carbon tax now,” he said, again calling on the opposition to support the repeal.

But a spokesperson for Alcoa said at the time of the closure announcement that the carbon tax – expected to be repealed later in the year – “was not a factor in the decision to close the Port Henry smelter or the rolled products business”.

And Treasury modeling of the former government’s carbon price found that aluminium smelting would decline by 61% over almost four decades – by 2050.