Independent Scotland would face £500 million EU bill

“But it is estimated that an independent Scottish state would contribute a total of around £11 billion to the EU budget over the same seven-year period."

He added that reduced subsidies for Scottish farmers under the EU’s common agricultural policy and lower structural funds would amount to another £1 billion.

The figures amount to a total shortfall to £500 million per year.

Brown also urged politicians to take the fight to rising nationalist and eurosceptic movements which took record numbers of seats at May’s European elections.

“The answer to nationalism is internationalism,” he said, adding that “better internationalism and EU global vision are the best way to combat extremism.”

“Nation states cannot solve the problems they face on their own.”

He told a packed audience, largely made up of MEPs and parliament officials, that the governments who had presided over the financial crisis were “guilty of failing to manage globalisation better”.

The former UK leader, himself a Scot, has largely withdrawn from front-line politics since his Labour government was defeated in 2010, but has emerged as an unlikely player in the referendum campaign.

The anti-independence No campaign brings together the Labour, Conservative and Liberal Democrat parties in an unlikely coalition called "Better Together".

Scotland’s 4 million voters will decide on 18 September on whether to leave the UK, with recent opinion polls indicating that the No campaign is marginally ahead but with a crucial 15 to 20 percent of voters undecided.

A spokesman for Scottish first minister Alex Salmond told the BBC also on Thursday that an independent Scotland would “make sure we get a far better deal - a better deal which Gordon Brown comprehensively failed to achieve for Scotland when he had the power to do so.”

“Our farmers have lost out on €1 billion as a result of Westminster's decisions on CAP funding”.

Salmond’s nationalist government is anxious to remain part of the European Union and says it would re-write and agree the country's new EU membership terms in the 18 months after Scotland becomes independent in 2016.

It believes it can secure their own EU budget rebate, larger in proportional terms than the UK’s.

It would also bid to gain opt-outs from the euro and the Schengen agreement on border-free travel.