SNP MP Brendan O'Hara was shouted down at Prime Minister's Questions as he attempted to discuss the topic of Scottish independence

As the benches erupted, O'Hara took his seat before being told to start again. The SNP MPs on the benches behind him looked appalled at the outburst.

"What a bunch of yobs" one SNP MP could be heard saying as O'Hara was called to begin again. 

He continued: "Thank you, Mr Speaker. Margaret Thatcher, John Major and his immediate predecessor all accepted ..."

Again, he faced roars from the House, but pushed on: "They all accepted that the Union of the United Kingdom can only be maintained by consent. Yet despite winning three elections seeking to test that consent, the Prime Minister insists that the SNP Government doesn't have a mandate to hold another independence referendum. 

WATCH: Ian Blackford clashes with Boris Johnson at PMQs

"So could he tell me exactly what mechanism is available to the Scottish people to give their consent or otherwise for maintaining this union and how should they go about exercising that."

Boris Johnson replied: "Well Mr Speaker I can only repeat my point, which is that the Scottish people do have a mechanism, they used it in 2014, it is a referendum and it took place, and it was – as members opposite confirmed – it was a once in a generation event."

Earlier in the day, Ian Blackford accused Boris Johnson’s Government of “disregarding” the Scottish Parliament.

Blackford asked: “Who should determine the future of Scotland? The Prime Minister or the people who live in Scotland?”

The Prime Minister used the same "once in a generation" answer.