Ukip leader Nigel Farage has insisted his party is relevant to Scottish politics as he prepares to target SNP voters in a Holyrood by-election.

The politician said membership is growing days before he is due to visit Edinburgh and announce who will stand in the Aberdeen Donside contest.

"We are growing in Scotland and have every intention of winning seats both at Holyrood and in next year's European elections north of the border. A fantasy? Not in the slightest," he said.

He dismissed the Edinburgh establishment as "divorced from reality" and claimed key Ukip issues such as migration resonate with the public more than mainstream parties think.

Aberdeen Donside appears solid SNP territory according to the 2011 Holyrood election, won by Brian Adam with 55% of the vote - almost double the vote taken by the nearest Labour challenger.

Mr Adam, who was suffering from cancer, died last month. The by-election will be held on June 20.

Mr Farage said he wants to explain to First Minister Alex Salmond why he thinks Ukip can make a dent in Scotland, despite his party polling a tiny 0.91% of the vote across Scottish regions in 2011.

"We are aiming to talk not to the rump of Scottish Tories, as he thinks, but specifically and deliberately at those he thinks of as his voters: patriotic Scots tired of his dissembling over Scotland and Europe," he wrote.

Mr Farage said independence from Europe should be considered before independence from Westminster."Otherwise it's merely changing cells in a constitutional Barlinnie," he wrote.

Failing to push for full independence would simply be "thin gruel", he added.

Attempts by Ukip to win a seat at Holyrood appear at odds with its 2010 general election manifesto, which pledged to replace the 129 MSPs with Scottish MPs.

The parliament would be retained, but on a part-time basis with MPs spending just one week a month on "devolved business" in Edinburgh and the rest of the time in London. English MPs would sit in special "English-only days" to give people south of the border a more distinct parliament, the party argued.

Ukip has also argued to downgrade powers held at Holyrood, arguing that all UK citizens should be entitled to equal treatment in health, education and public services.

Labour, the Conservatives and Liberal Democrats have already announced their candidates.

Labour has put forward city councillor Willie Young; the Conservatives confirmed their candidate as city councillor Ross Thomson, and the LibDems have chosen journalist and former special adviser Christine Jardine.

The SNP is expected to announce its candidate in the next few days, although it is widely tipped to be North East MSP Mark McDonald.

He would have to resign from his regional seat, allowing that vacancy to be filled automatically by another SNP candidate who stood in the last election, Christian Allard.

An SNP spokesman said: "As Ukip drags Westminster politics further and further to the right - and far away from Scotland's values - these ridiculous remarks from Nigel Farage underline exactly why Scotland needs to vote Yes and be an independent country.

"Ukip has never managed to move beyond the far fringes of politics in Scotland, and with daft comments like these it's not hard to see why.

"Mr Farage and his colleagues are an embarrassment to the rest of the No campaign. They are also a useful reminder to Scots of the dangers of a No vote in the independence referendum, which could see Scotland dragged to the exit door of the EU against our will."