As the seemingly irrepressible presidential campaign of Republican frontrunner Donald Trump shows no signs of running out of steam, the 69-year-old real estate mogul continues to receive an increasing number of attacks from his critics over his controversial views on subjects ranging from immigration to Isis.

Whilst he has so far taken all the barbs in his stride, he now faces his most influential critic yet in Pope Francis, the head of the 1.2 billion-strong Catholic Church.

In a freewheeling conversation on his flight home from a visit to Mexico on 17 February Francis told reporters, "A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian".

The pontiff's remarks were in regards to Trump's claim that if he became president he would build a wall between the United States and Mexico to keep out immigrants who entered illegally.

The comments have prompted the billionaire businessman to reprimand the religious leader as "disgraceful" for questioning his faith. In this video, IBTimes UK looks at the bitter war of words between the religious leader and US presidential hopeful.