The country would lose out on the UK’s annual £3 billion budget rebate and its EU structural funds slashed would be, leaving the newly-independent state up to £3.8bn worse off between 2014 and 2020, a coalition government report found.
However, the claims were dismissed by Nationalists, who said the former Tory leader was repeating the “same scare stores” as he did in 1997 when he warned Scotland would become a “high tax ghetto” after the Scottish Parliament was created.
Mr Hague launched a paper setting out the benefits of Scotland’s place in the UK ahead of the independence referendum on 18 September.
He warned that Scotland would only get a “fraction” of the global influence that it enjoys as part of the United Kingdom.
Mr Hague told an audience in Glasgow: “Being a member of this historic union gives people in Scotland the opportunity to do more good in the world, to exert an influence on global politics and economics.
“It gives the security of belonging to a nation of 63 million people and the fastest-growing economies in the western world and a tried-and-tested security network which is the envy of other nations and which will keep the Commonwealth Games safe this summer.
“It also provides a British passport, which provides instant access to our extensive diplomatic, consular and trade network and the most professional help worldwide for any Scot travelling or doing business overseas.
“Making a decision to remain in the United Kingdom is a positive choice, reinforcing what we already have and reaffirming what we can be if we continue to work together.”
The paper, titled Scotland Analysis: EU and International Issues, warned that Scotland’s net contribution to the EU would soar after independence.
The country would lose out on the current rebate of £3bn which the UK enjoys as well as about £200 million in structural funds between 2014-20.
Although the funding for agriculture is less clear, two case scenarios are presented for an independent Scotland’s overall EU budget position.
The worse scenario would leave it £3.8bn worse off over the 2014-20 period, about £1,470 for every man woman and child in Scotland, Treasury Secretary Danny Alexander said yesterday.
The better scenario would leave Scotland £1.9bn worse off, about £750 for every person, compared with its current position as part of the UK.
The SNP has proposed Scotland will enjoy a “seamless transition” to EU membership within 18 months, in time for independence being declared day in March 2016, but this was branded “unreasonable” by Mr Hague.
He also warned that Scotland would be forced to join up to euro currency and would face difficult talks to opt out of the Schengen free travel area.
Deputy First Minister Nicola Sturgeon branded Mr Hague an example of “the same old hypocritical Tories lecturing Scotland”.
“Let’s remember that he is the Tory politician who came to Scotland before devolution to scaremonger over what would happen if the Scottish Parliament was set-up,” Ms Sturgeon said.
“He claimed that four or five years into a Scottish Parliament, Scots would be living in a high-tax ghetto’.
“If we had listened to him then the Tories would now have free rein to privatise our NHS, impose tuition fees of £9,000 a year and cut police numbers.
“He was wrong then and he is wrong now.”
She added: “William Hague is the latest in a series of coalition ministers making flying visits to Scotland to lecture us on the dangers of independence.
“Yet none of them are actually prepared to debate – openly and directly – with Scottish ministers.”