Mhairi Black MP has never been one to mince her words, and she definitely didn't do that during a parliamentary debate.

The SNP MP for Paisley and Renfrewshire South has gone viral after eagle-eyed lipreaders noticed a rather cheeky - but hilarious - comment she made in reply to Tory Minister Caroline Nokes during a Westminster session.

Ms Black was criticising a move by the UK Government to withdraw housing benefits for 18 to 21-year-olds.

Ms Black started off by saying: “The Scottish Government cannot reverse the cut, or provide an exemption for Scotland.

“Does the minister agree that it is simply ridiculous that young people should suffer purely because this government is obsessed with imposing austerity?”

However, Ms Nokes retaliated by saying: “The Scottish Government already has a wide range of powers which would enable them to alleviate the changes being proposed here.”

It was then that Ms Black could be seen mouthing something in return.

Twitter user Katie McGarvey was the first to put forward a theory on what the Scots MP said.

She tweeted: "No much of a lip-reader but definitely mouthing, 'you talk s**te, hen'. #proud"

The 22-year-old politician posted a short clip of the debate on Twitter, and the comment she made can be seen at around the 1:13 mark.