The parliamentary turf war between the SNP and Labour has continued with Nationalist MPs defying convention and sitting on the Opposition front bench in the House of Commons.

Pete Wishart, the MP for Perth, and his SNP colleague, Michelle Thomson, who represents Edinburgh West, were spotted next to Shadow Cabinet Ministers as MPs began the process of swearing in.

The move was in response to a refusal by veteran Labour left-wingers to give up their traditional seats in an area usually reserved for the third biggest party at Westminster; now the SNP with 56 Members.

On Monday, Labour backbencher Dennis Skinner, famously dubbed the Beast of Bolsover, refused to give up his seat on the neighbouring front bench.

Mr Wishart explained that SNP MPs had approached their Labour colleagues to point out, by tradition, these benches were used by the third party and that, thus, this was "our space". But Labour refused to agree and, subsequently, Nationalist MPs took seats on the Opposition front bench and in the rows behind, which normally would be occupied by Labour MPs.

The Perth MP told The Herald: "We want to sit around the table with Labour to sort this out. They have simply refused to have a meeting with us. There is precedent here for us sitting on those benches."

When asked if the turf war was childish, Mr Wishart replied: "Labour are taking our spaces. What are we supposed to do? Go sit at the back and shut up? No way."

Alex Salmond, the Nationalist grandee, accused Labour of being "silly" and that the row showed how the official Opposition had failed to come to terms with losing so many of their seats.

But a Labour source urged the SNP to "grow up". He added: "They're already alienating a host of people by their attitude; they should treat Parliament with respect."

Mr Wishart insisted that his colleagues would continue to seek a reasonable solution to the problem and were intent on securing seats by arriving at 8am each day to place so-called "prayer cards" on the desired benches. If no agreement with Labour is reached, this is due to happen when the Commons sits for its next set-piece event, the Queen's Speech, a week today.