Religious freedom charity Release International is calling on the Prime Minister to stand by what he says now he has a majority in the Commons.
In a statement to the Prime Minister, it asks him to protect Christians abroad in his time in office.
"We congratulate the Prime Minister on his success and renewed mandate," said CEO Paul Robinson.
"Release urges Mr Johnson's new government to keep its pledge to make the protection of religious freedom at the very heart of UK foreign policy."
The Conservative party manifesto for the General Election in December pledged to implement the recommendations of the Bishop of Truro's review into the Foreign Office response to persecuted Christians around the world.
The review, commissioned by former Foreign Secretary Jeremy Hunt, looked into countries where persecution was worst, such as Nigeria, Sri Lanka and Syria, and made recommendations to the department, such as to train civil servants in religious literacy and to only provide aid and trade to countries that have a good track record on religious freedom.
During the Conservative leadership race, Boris Johnson promised to stand up for those facing persecution.
The previous Conservative government also promised to protect Christians from growing persecution, with the then Foreign Minister Sir Alan Duncan welcoming the Bishop of Truro's persecution report in July.
He told the House of Commons: "The government has decided to accept every recommendation in full. We will put Freedom of Religion or Belief at the heart of FCO culture."
Paul Robinson said the new Government must not abandon their manifesto pledge in this area, saying: "Amid the election jubilation and the flurry to deliver Brexit, Release urges the new Conservative government to remember its promises to the persecuted.
"We are immensely grateful that the UK government has declared the world will no longer be able to turn a blind eye to discrimination against Christians."