UK Prime Minister Boris Johnson has spoken to Joe Biden for the first time since the new US president was inaugurated.

Johnson said on Twitter that he looked forward to "deepening the longstanding alliance" between the UK and the US as they drove a "green and sustainable recovery from Covid-19".

Biden was sworn in as president and Kamala Harris as vice-president in a ceremony in Washington on Wednesday.

The PM said their inauguration was a "step forward" for the US.

A Downing Street spokesman said Mr Johnson "warmly welcomed" the president's decision to rejoin the Paris Agreement on climate change and the World Health Organization - both abandoned by Mr Biden's predecessor, Donald Trump.

"The prime minister praised President Biden's early action on tackling climate change and commitment to reach net zero by 2050," the spokesman said.