With pollsters reporting the 'Yes' and 'No' campaigns are neck and neck, banks have been issuing warnings over the financial viability of a future independent Scotland.

The Swiss bank Credit Suisse has led the knife sharpening, issuing an admonitory note saying that Scotland could face a "deep recession" should its people vote to secede from the UK.

"The re-domiciling of the financial sector and UK public service jobs, as well as a legal dispute over North Sea oil, would further accelerate any downturn. In our opinion, as North Sea oil production slows, we estimate that the non-oil economy would need a 10% to 20% devaluation to restore competitiveness. This would require a 5% to 10% fall in wages, driven by a steep rise in unemployment," the bank's economists wrote.

The bank also predicts constitutional issues for an independent Scotland, as well as difficulties for the remainder of the UK in case of a 'Yes' vote.

"We believe a yes vote would result in a constitutional crisis until Scottish MPs are excluded from Westminster. When they are, the Conservatives would have an ongoing electoral advantage in the UK," analysts wrote.

A TNS poll has shown that 51% of voters plan to vote 'No', with 51% voting 'Yes'. Over the weekend, a YouGov poll showed that the 'Yes' campaign held a marginal lead, as Scotland prepares to head to the polls on 18 September.

It's inspired a spate of ominous reports and comments from the financial sector – which is lobbying hard for the "Better Together" campaign.

The French bank Société Générale warned over equity fund outflows, which have escalated as the referendum looms larger on the horizon.

"The UK is increasingly a case apart, with net inflows into UK mutual funds and ETFs falling far behind its European neighbours. UK bond funds have hardly seen any compensation for cumulative outflows since 2007 (still remaining $10bn short compared to pre-crisis levels). Meanwhile, net outflows from UK equity funds are accelerating, due to fears that in the event of a Yes vote for Scottish independence on 18 September, the UK could break away ('brexit') from the European Union," bank analysts wrote in a note.

Meanwhile the National Bank of Australia has been warned that it could face a £62.7m bill should there be a 'Yes' vote. The owner of the Clydesdale Bank could be faced with higher bad debt charges and a struggle to offload its Scottish investment, Credit Suisse (again) warned.

Clydesdale is Scotland's third largest lender and analysts have warned that it could relocate to London if Scotland leaves the UK.