Pope Francis has opened the door for women who have received abortions – an act considered a grave sin by the Catholic church – to be absolved if they express contrition and seek forgiveness from their priest.

“The forgiveness of God cannot be denied to one who has repented,” the pontiff wrote in an extraordinary letter that was released by the Vatican on Tuesday.

“I am well aware of the pressure that has led them to this decision. I know that it is an existential and moral ordeal,” he added.

The extraordinary order by Francis, which temporarily allows all priests to grant forgiveness to women who have elected to have an abortion and regret the procedure, is part of the church’s jubilee year of mercy, which begins on 8 December and runs until 20 November 2016.

Within an hour of releasing the letter, the Vatican released another statement in response to a flood of queries, emphasising that the church did not “condone abortion nor minimise its grave effects”.

“The newness [of the order] is clearly Pope Francis’s pastoral approach,” the Vatican said. “Many bishops have granted priests permission to forgive the sin. The fact that this statement is coming from the pope in such a moving, pastoral way, is more evidence of the great pastoral approach and concern of Pope Francis.”

The church added that the fact that faithful people already went to confession to confess their abortions and other “grave sins” was a cause to thank God and to put in practice the mission of the church to “seek out those who were lost”.

The letter will be seen as further evidence that Francis, the first Latin American pope, is approaching his papacy as a liberal-minded reformer and is seeking to reach out to Catholics who believe the church – and its usually uncompromising attitudes towards abortion, homosexuality and divorce – is out of touch with modern social views.

Francis has already frustrated some traditional and conservative Catholics – particularly in the US – with his strong views against unfettered capitalism, which he has called “the dung of the devil”, as well as his call for action to combat global warming and phase out the use of fossil fuels. He made waves early on in his papacy when, in response to a question about a Vatican official who was allegedly gay, he responded: “Who am I to judge?”

Under canon law, doctors who perform abortions – or anyone involved in the procedure – are automatically excommunicated, according to Teresa Berger, a professor at Yale University’s divinity school.

But, under normal circumstances, those who face excommunication can be absolved if their confessor has received special authority from a bishop to do so – an authority that not all priests have.

In his letter, Francis said a “widespread and insensitive mentality” had led to the loss of proper personal and social sensitivity.

“The tragedy of abortion is experienced by some with a superficial awareness, as if not realising the extreme harm that such an act entails. Many others, on the other hand, although experiencing this moment as a defeat, believe that they have no other option,” he wrote.

Women who receive abortions are not the only people who will receive special clemency as part of the jubilee year. In his letter, the pope also granted special forgiveness to followers of the Society of St Pius X, known as Lefebvrists, a breakaway conservative order describing themselves as a “resistance movement” against the Vatican.

Francis said he had heard from several bishops of some followers’ “good faith and sacramental practice” and that, “motivated by the need to respond to the good of these faithful”, those who approached priests of the rebel authority to receive forgiveness shall be absolved of sins.