A Downing Street spokesperson said:
The Prime Minister held a telephone call with the new Prime Minister of Iraq, Adil Abdul Mehdi, this afternoon to congratulate him on taking office.
They agreed to continue to work together as Prime Minister Mehdi aimed to build a successful future for the people of Iraq.
They agreed the UK and Iraq were significant security partners, particularly in the ongoing fight against Daesh.
They noted that Iraq had an important role to play in the region.
They looked forward to meeting in the future.