LONDON — Scottish leader Alex Salmond warned on Monday that British politicians risk provoking a backlash in Scotland by running a negative campaign against independence and refusing to let Scots keep the pound if they vote to go it alone.

Salmond is fighting a closely choreographed attempt by London to scupper Scotland's Sept. 18 vote for independence by undermining his central economic case that Scotland could be a prosperous, independent nation.

Salmond accused Westminster of launching a "diplomatic offensive" against independence and of trying to "dictate from on high" after the three main UK parties joined forces to rule out a currency union with an independent Scotland.

"It is a sign of how out-of-touch and arrogant the Westminster establishment has become," Salmond told business leaders in Aberdeen, adding that it was to the benefit of both sides of the border to have a shared currency.

"No one doubts that Scotland can be a successful, independent country ... the issue is not whether we could be independent, but if we should be independent."

The twin pillars of Salmond's plan for independence — keeping the pound and negotiating European Union membership — have been shaken in recent days.

British finance minister George Osborne warned last week that Scotland could not keep the pound if Scots vote for independence while European Commission President Jose Manuel Barroso cautioned Scotland on Sunday that it would struggle to gain European Union membership.

Salmond downplayed Barroso's comments by saying no EU member state had indicated it would seek to block Scottish membership, particularly as Scotland was an eager member of the bloc, unlike the rest of the UK which is debating a vote on EU membership.

He described the tough tone from London as "campaign rhetoric" but said it would be a totally different picture if Scotland did vote for independence in seven months' time.

"What is said by Westminster during the heat of a campaign will be different from the reality of life" after a vote for independence, Salmond said, dubbing London's campaign against Scottish independence as "Project Fear".