Some of Scotland's largest financial groups have rallied together to support the country breaking away from the UK despite myriad reports warning against the move.

In an open letter to the Financial Times, the Royal Bank of Scotland's (RBS) former boss and chairman of Toscafund, George Mathewson, as well as five others said they support Scottish independence, even if it means it is likely that the country would lose its European Union (EU) membership.

The group's letter addresses a briefing paper from Scottish Financial Enterprise (SFE), an industry body representing Scotland's banks and insurance companies, which states that higher costs and complexity would hamper competitiveness following independence.

The letter states that the SFE's views have not been fully endorsed by its board and "do not reflect the balance of opinion in the Scottish financial sector, nor provide an objective analysis of the opportunities and risks involved - whether a Yes or No vote is recorded".

"There are certainly opportunities to attract more jobs and investment to Scotland with the powers of independence and significant opportunities in an independent Scotland for financial services," states the letter.

Standard Life Bank's founder Jim Spowart, a former economic adviser at Standard Life, David Simpson, founder of MLI Partners Frank McKirgan, and James Scott, a former director of industry group Scottish Financial Enterprise all signed the letter too.

The group stressed that these views were personal.

Scottish people will vote in an independence referendum on 18 September this year and will be asked the straight "yes/no" question: "Should Scotland be an independent country?"

The Scottish National Party (SNP) has repeatedly promised voters that if it breaks the 307-year union with England, it will retain the pound, stay a member of the European Union, and still share a financial industry regulators and laws.

However, UK and EU politicians, independent experts and a raft of firms have all said it is unlikely that any of these promises will be fulfilled.

The Confederation of British Industry launched a scathing attack on the SNP's economic plan, in the event the country breaks away from the UK, by saying it "doesn't add up."

The CBI said in a detailed report that, even taking into account oil and gas revenues, the SNP's economic plans and promises do not make sense, when looking at the numbers.

At the end of February, a poll revealed that a majority of Britain's biggest business leaders are against Scotland exiting the UK as independence would have a negative impact on companies.

According to a survey by recruitment firm Korn Ferry, 65% of the 32 FTSE100 companies polled said it would be "particularly bad for the Scots, not good for the English and would dilute the UK's economic influence".

Mathewson said the UK government for using "fear" tactics to sway voters.

According to a recent YouGov poll, 40% of the respondents said that UK Chancellor George Osborne was being sincere when he warned that an independent Scotland could not share sterling.

However, 45% of the respondents said they thought the Conservative MP and other Westminster politicians are deploying the warning as an empty threat, designed to win support for the "no" campaign.