Liberal Democrats have won "real economic credibility" and should be proud of their achievements in the coalition Government, chief secretary to the Treasury Danny Alexander said today.
In a defiant opening speech to the party's spring conference in Inverness, Mr Alexander underlined the Lib Dems' role in shaping UK economic policy.
The Highlands MP urged the party faithful to ignore opponents, adding: "Be proud because we are delivering big changes that are making a real difference to the lives of people in every corner of the United Kingdom.
"Ignore our opponents. We have nothing to apologise for, and a record to shout about."
Mr Alexander highlighted investment in broadband, efforts to save cross-border sleeper train services, a cut to fuel costs and changes to the income tax threshold.
Looking to the next general election, he told the conference he wants to push ahead with a pledge to raise the tax bar further from £10,000 to £12,500.
Mr Alexander, speaking at the Eden Court theatre, criticised his political opponents north and south of the Scottish border.
He said the first priority is to clean up Labour's "mess".
"Our plan has real credibility. It is keeping our interest rates at record lows, helping keep people in their homes, businesses in funds," he said.
"We can see from other countries the catastrophic damage done when governments don't have, or stick to, a clear and credible plan.
"That's not to say everyone agrees.
"Labour wants a plan B - more borrowing and debt. The B could be for Balls or Berlusconi, same difference.
"The SNP wants a plan MacB. They should have called it plan Mac-tripleB, because that's what it would do to our country's credit rating.
"Neither of them has economic credibility. We do."
He said there are strict limits to what he can say on tax with just weeks before the UK Budget.
Mr Alexander criticised the SNP for trying to separate Scotland from the rest of the UK, and suggested that they are doing this both politically and logistically.
He accused the Scottish Government of an ideologically driven attempt "to undermine the Caledonian sleeper".
He said: "The £50 million we offered shamed Alex Salmond and the SNP into more than matching it, and over the coming years we will see the most substantial investment this vital link has seen for decades.
"Yes, it shows what Scotland's two governments can deliver when they work together."
He added: "Now we need to stop the SNP's ideological attempt to cut off the north of Scotland's direct rail links to London in the daytime."
He said Scottish First Minister Alex Salmond is "a former banker still going around hawking a get rich quick scheme for the people of Scotland that we know won't work".
He added: "Mr Salmond was recently endorsed by (News Corporation chairman) Rupert Murdoch. I'm told he promised him 'the Sun will come out every day if you vote for separation'.
"This is the most serious debate for our nation's future for decades, possibly ever.
"We were right to bring the referendum issue to a head in January, and (Scottish Secretary) Michael Moore has played a blinder, his patience and reason winning the argument in recent weeks.
"In the coming months, we will be working with others to set out the positive economic case for the United Kingdom.
"But the extended uncertainty the SNP want is in itself damaging Scotland. As Scottish and Southern Electricity (SSE) pointed out last week, real investments in our vital renewables sector is being held back.
"And their fears are echoed by many businesses in many sectors across Scotland and beyond by international investors."
Last week, SSE published its response to the referendum consultations currently under way at Holyrood and Westminster, and stated that the referendum "does not mean that SSE will not invest in projects in Scotland while its future is being determined".
However, it said it has "no alternative" but to take "the additional risk of regulatory and legislative change" into account in making final investment decisions.
Mr Alexander went on to once again criticise the timing of the Scottish independence referendum, with the SNP lining up the "possible" date of October 18, 2014.
Mr Alexander said: "I really don't see why we have to wait until a Saturday in the school holidays in October 2014 to answer the single question - separation, Yes or No?
"The referendum could easily be organised next year, and there would be plenty of time to have a full debate.
"The timing of the referendum should not be dictated by the SNP's political interest, but by Scotland's national interest."
Mr Alexander also criticised the Scottish Government demand for devolution of the Crown Estate, which controls the UK's coastal revenues.
He said: "We have established a new coastal communities fund, so that for the first time those areas can share in the benefit that the Crown Estate receives from our marine resources.
"Not devolved to Edinburgh to be lost in some central fund - but made available to the communities themselves, from this April onwards."
The Lib Dems appeared to suffer a backlash for entering a coalition with the Conservatives at Westminster when Scotland went to the polls last year. Just five MSPs were returned to the Scottish Parliament.
The party failed to win any first-past-the-post Holyrood constituencies on the mainland, prompting Shetland MSP Tavish Scott to step down as Scottish leader.
He was replaced by newly elected MSP Willie Rennie, who previously served for about four years as MP for Dunfermline and West Fife.
In his conference speech today, Mr Alexander said: "Willie and his team are making a big mark on the Scottish Parliament, even if their numbers are small."
He added: "Thank goodness for Willie Rennie, who is the strongest, clearest and most powerful opposition voice in the Scottish Parliament. Thank goodness for his strong liberal voices in Holyrood."
Other speakers on day one of the three-day conference include Deputy Prime Minister Nick Clegg and Business Secretary Vince Cable.
The Deputy Prime Minister has pledged to expand on plans for a "green economic renaissance" while offering "practical help" through taxation.