Foreign Secretary Boris Johnson is making the UK a "laughing stock", the SNP's Westminster leader has claimed.

Ian Blackford described Johnson as "bumbling" after the Conservative cabinet minister said a solution to the Irish border issue could be found in the same way that London boroughs handle the congestion charge.

Johnson made the remarks after a letter he sent to the Prime Minister downgrading the severity of the issues created by a hard border on the island of Ireland was obtained by Sky News.

Blackford brought Johnson's comments to Theresa May's attention at Prime Minister's Questions on Wednesday.

He said: "The Foreign Secretary compared crossing the Irish border to going between Camden and Westminster, frankly you could not make this stuff up.

"This is a UK Government that is prepared to put in jeopardy the Good Friday Agreement. Does the Prime Minister agree with her bumbling Foreign Secretary who is making the UK a laughing stock?"

Theresa May rejected any assertion that she would damage the 1998 peace agreement struck in Northern Ireland.

The Prime Minister responded: "Indeed we made sure that that commitment was included in the joint report that we agreed with the EU last December, so that commitment to the Belfast Agreement stands and we are committed to the Belfast Agreement and the institutions under the Belfast Agreement."

She added: "Of course I continue to stand by wanting to ensure that all parts of the UK continue to flourish.

"I think the best way of doing that is ensuring all parts of the UK remain in the UK."