The rise in support for Scottish independence was holding steady prior to Westminster's outright rejection of a currency union, a poll suggests.

Some 29% of respondents said they will vote Yes against 42% who will vote No, with 29% remaining undecided, according to a TNS poll conducted in the first week of February.

The results are identical to a TNS poll in mid-January which revealed a swing from undecided towards independence, up to 29% from 27% in December and 26% in November, while support for the union remained at around 42%.

Two-fifths (40%) of decided respondents back independence against three-fifths (60%) who back the UK.

However, TNS has advised that the poll was conducted one week before the three main UK parties rejected the SNP's plan for a currency union and European Commission president Jose Manuel Barroso said it would be "difficult, if not impossible" for an independent Scotland to join the EU.

TNS head in Scotland Tom Costley said: "The debate on independence has stepped up a gear in the last few days.

"Opinion in Scotland showed little change over the last few months, with a relatively high level of don't knows, and our polls have consistently shown that people are looking for more information on which to make their decision.

"It may be that the recent activity, especially the firm statement by the anti-independence parties on the future of the pound, will stimulate more debate, bring out more information and help undecided voters to make up their minds."

Scottish philanthropist Sir Tom Hunter said the referendum was "way closer to call than anyone thinks" when he released his TNS poll of 1,054 people on February 2, revealing Scottish opinion between January 14 and 20.

His numbers were identical to the TNS poll of 996 people released today, conducted between January 28 and February 6.

Eleven days after Mr Hunter's poll was released, Chancellor George Osborne said: "The Scottish Government says that if Scotland becomes independent there will be a currency union and Scotland will share the pound. People need to know - that is not going to happen."

His view was echoed by Labour shadow chancellor Ed Balls and Liberal Democrat Chief Secretary to the Treasury Danny Alexander.

Three days later, Mr Barroso said: "It will be extremely difficult to get the approval of all the other member states to have a new member coming from one member state.

"It's going to be extremely difficult, if not impossible, a new member state coming out of our countries getting the agreement of the others."