Sharing the news on Instagram, Mrs Johnson said she had felt "pretty exhausted" for the past eight months but "we can't wait to meet this little one" in a few weeks' time.

The couple, who married in May 2021, already have two children - three-year-old Wilf and two-year-old Romy.

Mr Johnson has four children from his previous marriage to Marina Wheeler.

Writing on Instagram, Mrs Johnson said: "Wilf is v excited about being a big brother again and has been chattering about it nonstop.

"Don't think Romy has a clue what's coming…She soon will!"

Mr Johnson, who left Downing Street in September, became the first prime minister to marry while in office for nearly 200 years.

It was his third marriage, having previously been married to Ms Wheeler with whom he had four children. Their divorce was finalised in 2020. He has a further child from an affair.

He did not have any children with his first wife Allegra Mostyn-Owen.

In an interview in 2021, Mr Johnson said it was "fantastic" living with a baby in No 10 but "a lot of work".