The UK's defence secretary Michael Fallon was forced to cut short an interview when pressed to guarantee that valuable defence contracts would remain in Scotland.

Fallon was in Govan on Friday to announce that the construction of eight Type 26 frigates would commence on the Clyde next summer.

His media assistant was forced to jump in and curtail and interview with STV's political editor Bernard Ponsonby, however, after he failed to offer a guarantee of the contract remaining in Scotland, regardless of constitutional change.

When asked about the UK Government's right to withdraw the multi-billion pound contracts in the event of a second independence referendum, Fallon responded: "We are not anticipating any constitutional change in Scotland.

"We respect the decision of Scotland to stay within the United Kingdom and that is why we're investing in defence here."

Ponsonby pressed Fallon further, asking for a "cast-iron guarantee that this work will be here irrespective of any vote on independence," before being told to move on by the defence secretary's media assistant.

When repeatedly told to curtail his line of questioning, Ponsonby turned the camera on Fallon's assistant, asking her "do you want to do the interview instead?"

Ponsonby asked a final time about potential clauses in the contracts allowing the UK Government to move the work in the event of constitutional change, prompting Fallon's assistant to abruptly end the interview.

The vessels were promised by David Cameron during the independence referendum and were seen as an inducement to get Scots to vote No.

The programme, initially for the construction of 13 frigates, was later scaled down to eight, giving rise to accusations of backtracking from the UK Government.

Visiting BAE Systems' shipyard in Govan on Friday, Fallon announced that the first steel would be cut for the new contracts in the summer of 2017.